Records with Keyword: Computational Fluid Dynamics
Showing records 51 to 75 of 655. [First] Page: 1 2 3 4 5 6 7 Last
Review of Wind Turbine Icing Modelling Approaches
Fahed Martini, Leidy Tatiana Contreras Montoya, Adrian Ilinca
April 25, 2023 (v1)
Keywords: Computational Fluid Dynamics, icing simulation, modelling of ice accretion, wind turbine icing
When operating in cold climates, wind turbines are vulnerable to ice accretion. The main impact of icing on wind turbines is the power losses due to geometric deformation of the iced airfoils of the blades. Significant energy losses during the wind farm lifetime must be estimated and mitigated. Finding solutions for icing calls on several areas of knowledge. Modelling and simulation as an alternative to experimental tests are primary techniques used to account for ice accretion because of their low cost and effectiveness. Several studies have been conducted to replicate ice growth on wind turbine blades using Computational Fluid Dynamics (CFD) during the last decade. While inflight icing research is well developed and well documented, wind turbine icing is still in development and has its peculiarities. This paper surveys and discusses the models, approaches and methods used in ice accretion modelling in view of their application in wind energy while summarizing the recent research fin... [more]
Numerical Investigation of the Performance of a Submersible Pump: Prediction of Recirculation, Vortex Formation, and Swirl Resulting from Off-Design Operating Conditions
Virgel M. Arocena, Binoe E. Abuan, Joseph Gerard T. Reyes, Paul L. Rodgers, Louis Angelo M. Danao
April 24, 2023 (v1)
Keywords: Computational Fluid Dynamics, intake structure, mixed-flow pumps, performance, Q-H, sumps
Like any other turbomachinery, it is essential that the hydraulic behavior and performance of mixed-flow pumps are evaluated way in advance prior to manufacturing. Pump performance relies heavily on the proper design of the intake structure. Intake structures should be accurately designed in order to minimize and avoid unnecessary swirl and vortex formations. Ensuring the optimum performance condition as well as predicting how a particular intake structure affects the efficiency of the pump often requires either physical model studies or theoretical evaluations. Unfortunately, physical models are costly, time-consuming, and site-specific. Conversely, design and performance predictions using a theoretical approach merely gives performance values or parameters, which are usually unable to determine the root cause of poor pump performance. This study evaluates the viability of using Computational Fluid Dynamics (CFD) as an alternative tool for pump designers and engineers in evaluating pu... [more]
Numerical Study and Experimental Validation of Skim Milk Drying in a Process Intensified Counter Flow Spray Dryer
Umair Jamil Ur Rahman, Artur K. Pozarlik
April 24, 2023 (v1)
Keywords: Computational Fluid Dynamics, counter-current mechanism, experimental validation, Process Intensification, REA, skim milk, spray drying
This research presents 3D steady-state simulations of a skim milk spray drying process in a counter-current configuration dryer. A two-phase flow involving gas and discrete phase is modeled using the Eulerian−Lagrangian model with two-way coupling between phases. The drying kinetics of skim milk is incorporated using the Reaction Engineering Approach. The model predictions are found to be in accordance with the experimental temperature measurements with a maximum average error of 5%. The validated computational model is employed further to study the effects of nozzle position, initial spray Sauter Mean Diameter (SMD), air inlet temperature, and feed rate on the temperature and moisture profiles, particle impact positions, drying histories, and product recovery at the outlet. The location of the nozzle upwards (≈23 cm) resulted in maximum product recovery and increased the mean particle residence time at the outlet. A similar trend was observed for the highest feed rate of 26 kg/h owing... [more]
Measurement and Simulation of Flow in a Section of a Mine Gallery
Jakub Janus, Jerzy Krawczyk
April 24, 2023 (v1)
Keywords: Computational Fluid Dynamics, laser scanning, numerical model geometry
Research work on the air flow in mine workings frequently utilises computer techniques in the form of numeric simulations. However, it is very often necessary to apply simplifications when building a geometrical model. The assumption of constant model geometry on its entire length is one of the most frequent simplifications. This results in a substantial shortening of the geometrical model building process, and a concomitant shortening of the time of numerical computations; however, it is not known to what extent such simplifications worsen the accuracy of simulation results. The paper presents a new methodology that enables precise reproduction of the studied mine gallery and the obtaining of a satisfactory match between simulation results and in-situ measurements. It utilises the processing of data from laser scanning of a mine gallery, simultaneous multi-point measurements of the velocity field at selected gallery cross-sections, unique for mine conditions, and the SAS turbulence mo... [more]
Hydrodynamic Efficiency Analysis of a Flexible Hydrofoil Oscillating in a Moderate Reynolds Number Fluid Flow
Paul Brousseau, Mustapha Benaouicha, Sylvain Guillou
April 24, 2023 (v1)
Keywords: Computational Fluid Dynamics, deformable hydrofoil, fluid-structure interactions, NACA0015, oscillating hydrofoil, renewable marine energy
The paper focuses on the study of a semi-activated system, based on a combination of two movements of forced pitching and free-heaving motion. Therefore, quantifying with accuracy the hydrodynamic forces applied on the hydrofoil seems to be crucial. This is investigated throughout a numerical analysis of the hydrofoil dynamics. The deformable structure is oscillating in a low-Reynolds number flow. In this study, a hydrofoil animated by a combined forced pitching and heaving movements is considered. Various materials of the hydrofoil structure are studied, from the rigid material to a more flexible one. A partitioned implicit coupling approach is applied in order to consider the Fluid-Structure Interaction (FSI) effects, while the Navier−Stokes equations are solved using the Arbitrary Lagrangian−Eulerian (ALE) method. Both the viscous incompressible Navier−Stokes equations and the elasticity equation are solved using finite volume method. The study is based on the analysis of the hydrod... [more]
Multiparameter Optimization of Thrust Vector Control with Transverse Injection of a Supersonic Underexpanded Gas Jet into a Convergent Divergent Nozzle
Vladislav Emelyanov, Mikhail Yakovchuk, Konstantin Volkov
April 24, 2023 (v1)
Keywords: Computational Fluid Dynamics, engine, jet, nozzle, Optimization, thrust vector control
The optimal design of the thrust vector control system of solid rocket motors (SRMs) is discussed. The injection of a supersonic underexpanded gas jet into the diverging part of the rocket engine nozzle is considered, and multiparameter optimization of the geometric shape of the injection nozzle and the parameters of jet injection into a supersonic flow is developed. The turbulent flow of viscous compressible gas in the main nozzle and injection system is simulated with the Reynolds-averaged Navier−Stokes (RANS) equations and shear stress transport (SST) turbulence model. An optimization procedure with the automatic generation of a block-structured mesh and conjugate gradient method is applied to find the optimal parameters of the problem of interest. Optimization parameters include the pressure ratio of the injected jet, the angle of inclination of the injection nozzle to the axis of the main nozzle, the distance of the injection nozzle from the throat of the main nozzle and the shape... [more]
Investigations of Flow and Heat Transfer Characteristics in a Channel Impingement Cooling Configuration with a Single Row of Water Jets
Min-Seob Shin, Santhosh Senguttuvan, Sung-Min Kim
April 24, 2023 (v1)
Keywords: Computational Fluid Dynamics, confined array jets, heat transfer coefficient, jet impingement
The present study experimentally and numerically investigates the effect of channel height on the flow and heat transfer characteristics of a channel impingement cooling configuration for various jet Reynolds numbers in the range of 2000−8600. A single array consisting of eleven jets with 0.8 mm diameter injects water into the channel with 2 mm width at four different channel heights (3, 4, 5, and 6 mm). The average heat transfer coefficients at the target surface are measured by maintaining a temperature difference between the jet exit and the target surface in the range of 15−17 °C for each channel height. The experimental results show the average heat transfer coefficient at the target surface increases with the jet Reynolds number and decreases with the channel height. An average Nusselt number correlation is developed based on 85 experimentally measured data points with a mean absolute error of less than 4.31%. The numerical simulation accurately predicts the overall heat transfer... [more]
A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine
Clemens Gößnitzer, Shawn Givler
April 21, 2023 (v1)
Keywords: combustion, Computational Fluid Dynamics, cycle-to-cycle variations, internal combustion engine, RANS simulation
Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier−Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are ta... [more]
Surrogate-Based Optimization of Horizontal Axis Hydrokinetic Turbine Rotor Blades
David Menéndez Arán, Ángel Menéndez
April 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, design, hydrokinetic turbine, marine turbine, surrogate-based optimization
A design method was developed for automated, systematic design of hydrokinetic turbine rotor blades. The method coupled a Computational Fluid Dynamics (CFD) solver to estimate the power output of a given turbine with a surrogate-based constrained optimization method. This allowed the characterization of the design space while minimizing the number of analyzed blade geometries and the associated computational effort. An initial blade geometry developed using a lifting line optimization method was selected as the base geometry to generate a turbine blade family by multiplying a series of geometric parameters with corresponding linear functions. A performance database was constructed for the turbine blade family with the CFD solver and used to build the surrogate function. The linear functions were then incorporated into a constrained nonlinear optimization algorithm to solve for the blade geometry with the highest efficiency. A constraint on the minimum pressure on the blade could be set... [more]
Numerical Simulation of a Novel Dual Layered Phase Change Material Brick Wall for Human Comfort in Hot and Cold Climatic Conditions
Atiq Ur Rehman, Shakil R. Sheikh, Zareena Kausar, Sarah J. McCormack
April 21, 2023 (v1)
Keywords: Ansys, buildings, Computational Fluid Dynamics, latent heat, phase change material (PCM), phase change simulations, summer and winter, thermal energy storage (TES)
Phase change materials (PCMs) have a large number of applications for thermal energy storage (TES) and temperature reduction in buildings due to their thermal characteristics and latent heat storage capabilities. The thermal mass of typical brick walls can be substantially increased using a suitable PCM primarily based on phase change temperature and heat of fusion for different weather conditions in summer and winter. This study proposed a novel dual-layer PCM configuration for brick walls to maintain human comfort for hot and cold climatic conditions in Islamabad, Pakistan. Numerical simulations were performed using Ansys Fluent for dual PCMs layered within a brick wall for June and January with melting temperatures of 29 °C and 13 °C. This study examined and discussed the charging and discharging cycles of PCMs over an extended period (one month) to establish whether the efficacy of PCMs is hindered due to difficulties in discharging. The results show that the combined use of both P... [more]
Validation of Modified Algebraic Model during Transitional Flow in HVAC Duct
Konrad Nering, Krzysztof Nering
April 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, HVAC duct, numerical simulation, OpenFOAM, PTV, steady-state transitional flow
Airflow occurring in a ventilation duct is characterized by low velocity and hence low Reynolds number. In these conditions, either a laminar, transitional or turbulent flow will occur. Different flow conditions result in different values of the friction coefficient. To achieve the transitional flow in numerical simulation, a modified algebraic model for bypass transition (modified k−ω) was used. Numerical simulation was validated using Particle Tracking Velocimetry (PTV) in the circular channel. The modified algebraic model consists of only two partial differential equations, which leads to much faster calculation than the shear stress transport model. Results of the modified algebraic model are largely consistent with either the measurement and shear stress transport model considering laminar and transitional flow. Consistency slightly decreased in turbulent flow in relation to the model using shear stress transport method.
Effect of Roof Cooling and Air Curtain Gates on Thermal and Wind Conditions in Stadiums for Hot Climates
Fangliang Zhong, Hassam Nasarullah Chaudhry, John Kaiser Calautit
April 21, 2023 (v1)
Keywords: air curtain, building energy simulation, Computational Fluid Dynamics, hot climates, stadium cooling, thermal comfort
To host the 2022 FIFA World Cup, Qatar is facing the greatest challenge in balancing the energy consumptions for cooling the stadiums and the thermal comfort for both players and spectators. Previous studies have not considered using a combined configuration of air curtain and roof cooling supply slot in stadiums to prevent the infiltration of outside hot air and reduce the cooling system’s energy consumption. This paper presents a Computational Fluid Dynamics (CFD) study of thermal and wind modeling around a baseline stadium and simulates the cooling scenarios of air curtains and roof cooling along with the energy consumption estimations for the World Cup matches using Building Energy Simulation (BES). Sensitivity analysis of different supply speeds and supply temperatures of air curtain gates and roof cooling was carried out, and the results showed that scenario six, which provides supply air of 25 m/s and 20 m/s at the roof and air curtain gates with a supply temperature of 10 °C, d... [more]
Investigations of Rake and Rib Structures in Sand Traps to Prevent Sediment Transport in Hydropower Plants
Mads Mehus Ivarson, Chirag Trivedi, Kaspar Vereide
April 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, hydropower, multiphase, particle, sand trap, sediment transport
In order to increase the lifespan of hydraulic turbines in hydropower plants, it is necessary to minimize damages caused by sediment erosion. One solution is to reduce the amount of sediments by improving the design of sand trap. In the present work, the effects on sand trap efficiency by installing v-shaped rake structures for flow distribution and rib structures for sediment trapping is investigated numerically using the SAS−SST turbulence model. The v-shaped rake structures are located in the diffuser near the inlet of the sand trap, while the ribs cover a section of the bed in the downstream end. Three-dimensional models of the sand trap in Tonstad hydropower plant are created. The present study showed that integrating rib type structure can reduce the total weight of sediments escaping the sand trap by 24.5%, which leads to an improved sand trap efficiency. Consequently, the head loss in the sand trap is increased by 1.8%. By additionally including the v-shaped rakes, the total we... [more]
Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions
Marcin Łęcki, Dariusz Andrzejewski, Artur N. Gutkowski, Grzegorz Górecki
April 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, heat exchanger, plate-fin tube, tube-fin contact
Plate fin-tube heat exchangers are widely used in air conditioning and refrigeration systems and other industry fields. Various errors made in the manufacturing process can result in the formation of an air gap between the tube and fin. Several numerical simulations were carried out for a symmetric section of plate fin-tube heat exchanger to study the influence of air gap on heat transfer under periodic flow conditions. Different locations and sizes of an air gap spanning 1/2 circumference of the tube were considered for the range of airflow velocities. Velocity and temperature fields for cases with air gap were compared with ideal thermal contact cases. Blocking of heat flow by the gap leads to the reduction of heat transfer rate. Fin discontinuity in the front of the tube causes the smallest reduction of the heat transfer rate in comparison to the ideal tube-fin contact, especially for thin slits. The rear gap position is the worst in the smallest gap range. Therefore, reversing the... [more]
Optimization of Air Cooling System Using Adjoint Solver Technique
Grzegorz Czerwiński, Jerzy Wołoszyn
April 21, 2023 (v1)
Keywords: adjoint method, Computational Fluid Dynamics, heat sink, heat transfer, pseudo-transient solver, shape optimization
Air cooling systems are currently the most popular and least expensive solutions to maintain a safe temperature in electronic devices. Heat sinks have been widely used in this area, allowing for an increase in the effective heat transfer surface area. The main objective of this study was to optimise the shape of the heat sink geometric model using the Adjoint Solver technique. The optimised shape in the context of minimal temperature value behind the heat sink is proposed. The effect of radiation and trapezoidal fin shape on the maximum temperature in the cooling system is also investigated. Simulation studies were performed in Ansys Fluent software using the Reynolds—averaged Navier−Stokes technique. As a result of the simulation, it turned out that not taking into account the radiation leads to an overestimation of temperatures in the system—even by 14 ∘C. It was found that as the angle and height of the fins increases, the temperature value behind the heat sink decreases and the hea... [more]
Combining Baffles and Secondary Porous Layers for Performance Enhancement of Proton Exchange Membrane Fuel Cells
Luka Mihanović, Željko Penga, Lei Xing, Viktor Hacker
April 20, 2023 (v1)
Keywords: baffle geometry optimization, biporous layer, Computational Fluid Dynamics, Forchheimer inertial effect, proton-exchange membrane fuel cells
A numerical study is conducted to compare the current most popular flow field configurations, porous, biporous, porous with baffles, Toyota 3D fine-mesh, and traditional rectangular flow field. Operation at high current densities is considered to elucidate the effect of the flow field designs on the overall heat transfer and liquid water removal. A comprehensive 3D, multiphase, nonisothermal computational fluid dynamics model is developed based on up-to-date heat and mass transfer sub-models, incorporating the complete formulation of the Forchheimer inertial effect and the permeability ratio of the biporous layers. The porous and baffled flow field improves the cell performance by minimizing mass transport losses, enhancing the water removal from the diffusion layers. The baffled flow field is chosen for optimization owing to the simple design and low manufacturing cost. A total of 49 configurations were mutually compared in the design of experiments to show the quantitative effect of... [more]
Effect of the Preheated Oxidizer Temperature on Soot Formation and Flame Structure in Turbulent Methane-Air Diffusion Flames at 1 and 3 atm: A CFD Investigation
Subrat Garnayak, Subhankar Mohapatra, Sukanta K. Dash, Bok Jik Lee, V. Mahendra Reddy
April 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, flamelet, pressure, soot, temperature
This article presents the results of computations on pilot-based turbulent methane/air co-flow diffusion flames under the influence of the preheated oxidizer temperature ranging from 293 to 723 K at two operating pressures of 1 and 3 atm. The focus is on investigating the soot formation and flame structure under the influence of both the preheated air and combustor pressure. The computations were conducted in a 2D axisymmetric computational domain by solving the Favre averaged governing equation using the finite volume-based CFD code Ansys Fluent 19.2. A steady laminar flamelet model in combination with GRI Mech 3.0 was considered for combustion modeling. A semi-empirical acetylene-based soot model proposed by Brookes and Moss was adopted to predict soot. A careful validation was initially carried out with the measurements by Brookes and Moss at 1 and 3 atm with the temperature of both fuel and air at 290 K before carrying out further simulation using preheated air. The results by the... [more]
Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon
Grzegorz Czerwiński, Jerzy Wołoszyn
April 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, evaporation, numerical model, thermal resistance, two-phase closed thermosyphon
With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation−condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medi... [more]
Analysis of the Velocity Distribution in the Plenum Box with Various Entries
Joanna Halibart, Klaudia Zwolińska, Marek Borowski, Marek Jaszczur
April 20, 2023 (v1)
Keywords: air distribution, Computational Fluid Dynamics, forced ventilation, PIV, plenum boxes
The ventilation system plays a crucial role in every building. Proper design and optimization of its operation increase the comfort of users due to efficient air exchange and at the same time control its velocity in the rooms. The aim of this paper is the analysis of the effect of plenum box entry on the velocity profile concerning the diffuser face panel. This issue may sometimes be ignored at the design stage but can significantly affect the airflow from the diffuser and consequently increase the risk of draft. The results of the PIV experimental measurements and numerical simulations concerning various entries of the plenum box (top and side) were investigated in this study. The measurements were used to develop the mathematical and numerical models, which were then used to assess the effect of localization of the spigot of the plenum box on its operation. The numerical analysis was carried out on plenum boxes with the air diffuser with a face panel composed of square grid perforati... [more]
Performance Improvement of a Double-Layer Microchannel Heat Sink via Novel Fin Geometry—A Numerical Study
Yong-Dong Zhang, Miao-Ru Chen, Jung-Hsien Wu, Kuo-Shu Hung, Chi-Chuan Wang
April 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, different geometry, double-layer microchannel heat sink, pumping power, response surface methodology, thermal resistance
This study proposes a novel design having dense fins with lesser thickness at the upper layer and comparatively spare fins with greater thickness in the lower layer to further improve the overall thermal performance of a double-layer microchannel heat sink. The design can effectively direct more low temperature fluid flow toward the lower layer to improve heat transfer while the sparse fin structure at low layer can ease pressure drop penalty. At the same time, the thicker fins at the lower layer ensure higher fin efficiency to facilitate high heat transfer. Parametric and detailed analysis is conducted for the proposed double-layer microchannel heat sink in comparison with the traditional one. After optimization, the thermal resistance of the proposed double-layer microchannel heat sink at the same pumping power is found to be reduced by 9.42% when compared to the traditional double-layer microchannel heat sink. Yet at the same Reynolds number, the Nusselt number of the proposed desig... [more]
The Steady Wake of a Wall-Mounted Rectangular Prism with a Large-Depth-Ratio at Low Reynolds Numbers
Arash Zargar, Ali Tarokh, Arman Hemmati
April 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, depth ratio, DNS, heat exchange, prism, wake dynamics, wall mounted
The wakes of wall-mounted small (square) and large (long) depth-ratio rectangular prisms are numerically studied at Reynolds numbers of 50−250. The large depth-ratio significantly alters the dominance of lateral secondary flow (upwash and downwash) in the wake due to the reattachment of leading-edge separated flow on the surfaces of the prism. This changes the wake topology by varying the entrained flow in the wake region and changing the distribution of vorticity. Thus, the magnitude of vorticity significantly decreases by increasing the prism depth-ratio. Furthermore, the length of the recirculation region and the orientation of near wake flow structures are altered for the larger depth-ratio prism compared to the square prism. Drag and lift coefficients are also affected due to the change of pressure distributions on the rear face of the prism and surface friction force. This behavior is consistently observed for the entire range of Reynolds numbers considered here. The wake size is... [more]
CFD Simulations for Performance Enhancement of a Solar Chimney Power Plant (SCPP) and Techno-Economic Feasibility for a 5 MW SCPP in an Indian Context
Arijit A. Ganguli, Sagar S. Deshpande, Aniruddha B. Pandit
April 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, discounted cash flow, heat transfer, solar chimney power plant, techno-economic feasibility
The use of solar energy for power generation using the innovative solar chimney concept has been explored by many researchers mostly with the help of analytical models as well as CFD simulations while experimental studies for a pilot and bench scale facilities have been carried out. The efficiencies of these chimneys, however, are less than 1% (~0.07% for 50 kW pilot plant similar to Manzanares plant in Spain). In the present study, an effort has been made to make modifications in the chimney design to improve the efficiency of the chimney in terms of power generation. CFD simulations have been carried out for this modified design and the efficiency is seen to improve to 0.12% for a 50 kW chimney. Furthermore, a techno-economic feasibility analysis has been carried out for a conventional 5 MW solar power plant which can be installed on the western part of India, which receives good solar irradiation throughout the year. Two cases with and without government subsidies have been consider... [more]
Experimental and CFD Investigation on the Application for Aerogel Insulation in Buildings
Santu Golder, Ramadas Narayanan, Md. Rashed Hossain, Mohammad Rofiqul Islam
April 20, 2023 (v1)
Keywords: aerogel, Computational Fluid Dynamics, decay, insulation, temperature
Reducing building energy consumption is a significant challenge and is one of the most important research areas worldwide. Insulation will help to keep the building’s desired temperature by reducing the heat flow. Additionally, proper insulation can provide an extended period of comfort, leading to reduced building energy requirements. Encapsulated air is the major aspect of most thermal insulation materials. Low thermal conductivity is a good characteristic of thermal insulation materials. Aerogel has low thermal conductivity, so it is suitable for glazing and insulation purposes. This research paper investigates the effectiveness of aerogel as an insulation material in buildings by incorporating a translucent aerogel-glazing system in the window and aerogel insulation in the wall of a building. Experimental investigation of a 10 mm thick aerogel blanket surrounded box was conducted to assess its performance. Additionally, a CFD simulation was conducted, and the results of temperature... [more]
Computational Flow Analysis on a Real Scale Run-of-River Archimedes Screw Turbine with a High Incline Angle
Dylan Sheneth Edirisinghe, Ho-Seong Yang, Min-Sung Kim, Byung-Ha Kim, Sudath Prasanna Gunawardane, Young-Ho Lee
April 20, 2023 (v1)
Keywords: Archimedes screw, Computational Fluid Dynamics, flow field, hydro, turbine
The Archimedes screw turbine (AST) is the most sustainable mini-hydropower extraction method that offers number of economic, social, and environmental advantages. Nowadays, many researchers are interested in AST development as it is considered a new technology. Currently, a lot of researchers are conducting experimental testing of the screws, comparing their reliability with computational fluid dynamic (CFD) analyses. Almost all of them are lab-scale testing models that claiming an average 80% efficiency for low pitch angles. In the case of a real site with a small inclination angle, the length of the screw is large enough to cause severe problems, specially related to bending of the screw. Therefore, this research was conducted to analyze the CFD flow field in a real site-scale AST with the maximum possible inclination of 45 degrees. In addition, the design was done without the upper and lower reservoir as it was conceived as a run-of-river flow system. The simulated real scale AST re... [more]
Impact of Enclosure Boundary Patterns and Lift-Up Design on Optimization of Summer Pedestrian Wind Environment in High-Density Residential Districts
Zhengrong Jiang, Weijun Gao
April 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, enclosure boundary, high-density residential district, lift-up design, pedestrian wind environment
A comfortable wind environment favors the sustainable development of urban residential districts and public health. However, the rapid growth of high-rise urban residential districts leads to low wind velocity environments in summer. This study examines the influence of enclosure boundary patterns and lift-up design on the wind environment and proposes an optimization strategy to improve the low wind velocity environment in residential districts in summer. A typical residential district in Hangzhou was selected; the average wind velocity, calm wind zone ratio and comfortable wind zone ratio were selected as the evaluation indexes. The wind environment for different enclosure boundary patterns and lift-up designs were obtained via computational fluid dynamics (CFD) simulations. The results indicate that the pedestrian wind environment is greatly improved in residential districts by reducing the height/width of the enclosure boundary, increasing the permeability rate and adopting a lift-... [more]
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