Volume 10: Fluids Engineering最新文献

{"title":"Computational Fluid Dynamics Modeling of the Efficacy of HVAC Adjustments on Mitigating Airborne Transmission of SARS-CoV-2","authors":"Jay H. Woo, Amal Bukhari, Louis Lane, Lutor Mei, Melody Baglione, P. Yecko, Scott Bondi","doi":"10.1115/imece2021-73727","DOIUrl":"https://doi.org/10.1115/imece2021-73727","url":null,"abstract":"\u0000 Assessing and improving the safety of social settings is pivotal for the reopening of facilities and institutions during the pandemic. Recent discoveries now suggest that the predominant medium of SARS-CoV-2 transmission is exposure to infectious respiratory aerosols. Airborne viral spread is particularly effective in indoor environments — which have been strongly implicated in high transmission rates and super-spreading events. This study focuses on computational fluid dynamics models developed to study the specific ventilation features of an indoor space and their effects on indoor particle spread. A case study is conducted on a typical classroom at the Cooper Union. Masked occupants are modeled in the room as aerosol sources to compare the performance of different ventilation settings on the exhaust rates of airborne particles. Simulation results reveal that increasing ventilation rates accelerate particle evacuation. Visualization and segregated data comparisons indicate regions of particle accumulation induced by the design and geometry of the classroom in relation to its occupants. Visualization is also used to observe a uniform distribution of airborne particles after only 10 minutes of simulated time — confirming the need for safety measures beyond the six feet distancing guideline.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124365046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep Learning for Drag Coefficient Predictions of Spherical and Non-Spherical Particles","authors":"Pratik Mahyawansi, Cheng-Xian Lin, Shu-Ching Chen","doi":"10.1115/imece2021-69010","DOIUrl":"https://doi.org/10.1115/imece2021-69010","url":null,"abstract":"\u0000 The drag model for non-spherical particles required in a particle-laden flow is not fully established, which could cover a wide range of sphericities. This study focuses on developing an artificial neural network model by using a large number of available experimental data for a wide range of sphericities (0.034–1), density ratios (0.0005–0.491), and Reynold numbers (0.002–79432). Available experimental and DNS data for particles of various sizes and materials tested against liquid and gas are identified to correlate the drag coefficient. Three different neural network algorithms, Random Forest, Gradient Boosting, and a Deep Neural Network (DNN), are trained and evaluated. The neural network results were compared to the experimental results and to select numerical correlations. It was found that the DNN model outperforms all the other methods and algorithms for most of the studied sphericities (0.36–1).","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131990630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance of a Two Stage Electrohydrodynamic Gas Pump With Different Polarities","authors":"A. K. M. Monayem H. Mazumder, Shariful A. Robin, Margaret Wood","doi":"10.1115/imece2021-71601","DOIUrl":"https://doi.org/10.1115/imece2021-71601","url":null,"abstract":"\u0000 In this study, fluid flow induced by a two stage electrohydrodynamic (EHD) gas pump in a square channel has been evaluated by experimental measurement and numerical simulations. This study is implemented by a two stage EHD gas pump with different polarities for 24 emitting electrodes configuration to seek the relation between the number of stages and polarities. The EHD pump is evaluated for a wide range of operating voltages starting from 20 kV up to 28 kV for further improvement in its performance. To achieve the maximum enhancement, the emitting electrodes of the EHD gas pump are flush mounted on the channel walls so that the corona wind produced directly disturbs the boundary layer thickness and improves the heat transfer. This is leading to a higher velocity near the channel walls and resulting in an inverted parabolic velocity profile at the center of the channel, which is opposite to the fully developed velocity profile of a forced flow. Velocities are measured at three cross-sections along the tube length and then integrated to obtain the volume flow rate. The results show that EHD technique has a great potential for many engineering applications.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"115 20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126373209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A New Variant of the Dynamic Hybrid RANS-LES Model for Complex Turbulent Flows","authors":"Tausif Jamal, Olalekan O. Shobayo, D. K. Walters","doi":"10.1115/imece2021-72185","DOIUrl":"https://doi.org/10.1115/imece2021-72185","url":null,"abstract":"\u0000 This study proposes a new variant of the Dynamic Hybrid RANS-LES (DHRL) model. Since the baseline DHRL model uses the ratio of resolved to modeled turbulent stress in RANS-to-LES blending, it was observed that for some types of flows the DHRL model remained in RANS mode despite the presence of appreciable levels of LES fluctuations. A new statistical variable is introduced in this study and implemented into a modified blending function to facilitate model transition from RANS to LES based on the presence of appreciable levels of resolved turbulence. Numerical simulations are carried out using the density-based finite-volume solver Loci-CHEM for canonical test cases such as fully developed channel flow, flow over a backward facing step, and flow over a three-dimensional axisymmetric hill. A comprehensive analysis of results indicate that the new model successfully addresses some of the shortcomings of the baseline DHRL model and it is concluded that new DHRL model variant is a useful alternative to traditional HRL models.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114173412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ventilation CFD Analysis at an Classroom as a Tool for Air Safety Verification Under COVID19 Context, a Case Study","authors":"Patrik Kehler, Carlos Chaves, Abdías García, Hugo Centurion, Alejandro Escobar, Logan Lopes, Santiago Aquino, Nicolás Ferreira, Jorge H. Kurita","doi":"10.1115/imece2021-73785","DOIUrl":"https://doi.org/10.1115/imece2021-73785","url":null,"abstract":"\u0000 The COVID 19 pandemic has struck the global economy and slowed down human activity. Paraguay, a small South-American country, was not an exception. This work results from the urgent need to reopen universities, schools, and other academic institutions to resume teaching activities in light of restrictive access to online learning in Paraguay. In order to contain the spread of this virus, school activities such as course lectures were placed on hold indefinitely. Inappropriate airflow in an enclosed space is one of the main factors in the spread of this virus. When combined with personal protective equipment, proper air ventilation and air replacement can significantly reduce this airborne virus’s spread. Potential sources of contaminant accumulation are stagnant locations of air in a closed volume. It is, therefore, essential to first identify these hot spots. Utilizing computational tools, such as CFD, an airflow analysis can be conducted to see any potential stagnant point. In the case of a classroom, it will then allow proper airflow by avoiding stagnant points by moving furniture, equipment, and chairs in combination to adding walls and opening windows and doors. This type of CFD study will set the benchmark for future classroom layout standards in this pandemic background. The work discussed here is a case study on a 300 student classroom at the Faculty of Engineering at the National University of Asuncion.\u0000 The CFD results showed detailed information on flow patterns and velocity profiles in the analyzed classroom environment and air cycle and exhaust results. The six air conditioning systems blowing 300 CFM each, combined with eight fans installed at the ceiling, forced air to recirculate and helped to remove old air to the windows and suction some new air from doors. This helped university administrators to reopen some class areas and keep their faculties and students safe for lectures. It is important to remark here that air reposition could be measured, showing 200 CFM air removal in this first simulation run. Further analysis with a different internal layout will be needed to see if any improvements can be made. It is expected to have a much better air removal by adding a localized exhaust fan. This work suggests the location of each location’s outlet points and flows capacity to ensure proper ventilation is achieved in this particular case study. Other academic institutions are showing interest in implementing this computational tool to design classroom layout as well as ventilation schemes.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"401 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115919715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Geometry on Small Scale Venturi Nozzle Performance","authors":"Hannah O’Hern, Xiang Zhang, Bahman Abbasi","doi":"10.1115/imece2021-68560","DOIUrl":"https://doi.org/10.1115/imece2021-68560","url":null,"abstract":"\u0000 A parametric study was conducted on small scale, subsonic Venturi nozzles. The purpose of this study was to determine the effect of different operating conditions and different geometric parameters on the performance of the nozzle. In this study, the performance of the nozzle was defined as the ratio of suction mass flow to motive mass flow, or the suction ratio. The parametric study included 15 different nozzle geometries, under various operating conditions, for a total of 55 case studies. The parametric study was conducted using CFD in Ansys Fluent. Additionally, experimental validation was conducted for several 3D printed nozzles. Dimensional analysis of the parameters was completed to determine the form of a dimensionless correlation for the suction ratio as a function of the other parameters. The case studies were run through a constrained multi-variable global optimization code to determine the dependency on each dimensionless group. This correlation can be used as a design guide for Venturi nozzles. If operating conditions dictate an optimum suction ratio, the ideal nozzle geometry can be determined. Alternatively, based on the geometry of a given nozzle, the resulting suction ratio can be determined.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"139 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122915771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design of a Hydrokinetic Turbine for Energy Ships Applications With Combined Extended Analytical Betz-Schmidt Method and Numerical Simulations CFD","authors":"P. Epple, Jonas Holzbrecher, M. Steppert, M. Platzer","doi":"10.1115/imece2021-70051","DOIUrl":"https://doi.org/10.1115/imece2021-70051","url":null,"abstract":"\u0000 The energy available for a sailing ship is a combination of wind energy and the energy in the water. The wind energy propels the ship blowing into the sail and in this way generates the thrust. The energy in the water can be transformed into electrical energy by means of a hydrokinetic turbine. The electrical energy can be stored in a battery or it can be converted into hydrogen by means of an electrolyzer. In such a combination the ship is called an energy ship.\u0000 In this work a new extended design method for the hydrokinetic turbine of the energy ship is presented and three different design variations based on Betz theory have been developed and verified with computational fluid dynamics CFD. The first Betz Standard (BS) design is based on the optimum turbine design according to Betz which is based on linear momentum theory. The second Betz Extended (BE) and third Propeller Like (PL) designs are also based on the theory of Betz but with an optimized extended airfoil length.\u0000 The theory and the design methods for each turbine are presented. The setup and the results of the numerical simulations are shown in detail and the advantages and disadvantages of each design method are discussed. Especially the different turbine characteristics, i.e. the axial force acting on the turbine, the torque and power including their dimensionless coefficients are analyzed and compared.\u0000 As an example, in a first analytical ideal design calculation according to the Betz theory, assuming a diameter of 890 mm and a ship velocity of 5.2 m/s, a power output of 25.8 kW was predicted for the BS design. With tip and profile losses the expected output is 21.9 kW. The results of the numerical calculation of the hydrokinetic turbine characteristics show that it has a typical behaviour as also found in wind turbines. The BS and BE design have its maximum power output near the design point at the design tip speed ratio λDBS = λDBE = 7. For the PL design λDPL is not known a priori but by means of the CFD results it is shown to be in the range of 4 < λDPL < 5. The BS design shows a maximum power output of about 17 kW with a power coefficient of cp = 0.4 at λOBS = 6.5. The BE and the PL designs show approximately the same maximum power output of about 21 kW with a power coefficient of cp ≈ 0.5 and hence are close to the predicted design output with losses. The BE and PL turbines show their maximum power output at λOBE = 5 respectively at λOPL = 4.2. However, the BE design has a much flatter power characteristics delivering the 21 kW over a much larger range of tip speed ratio, showing the advantage of this new design method. The extended airfoil surface of the BE design and the BS turbine design leads to a higher hydrodynamic resistance but also to a higher torque and power output. With those two designs, a power coefficient of almost 50% was achieved, quite close to the maximum theoretical possible power coefficient of Betz cp,Betz = 16/27 = 59.3%. Hence this is in the range a","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128845378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical Simulation of the Flow Inside a Horizontal Closed Refrigerated Display Cabinet","authors":"João Silva, Vitor Guedes, S. Teixeira, Pedro Lobarinhas, J. Teixeira, Nelson Rodrigues","doi":"10.1115/imece2021-73589","DOIUrl":"https://doi.org/10.1115/imece2021-73589","url":null,"abstract":"\u0000 A refrigerated display cabinet is a device often used to preserve the products contained inside while enabling the costumer to have a view to the products stored. The main objective of this work was to investigate, using the ANSYS Fluent software, the airflow in a horizontal closed refrigerated display cabinet to better understand the fluid flow behavior in its interior. The turbulent airflow and non-isothermal heat transfer process were computed in a 2D transient state mathematical model where the basic equations governing the transport phenomena inside of the refrigerated display cabinet were solved. Regarding the turbulence model, this was modeled with the three-equation model since it can address the boundary-layer transition regions within the cabinet. After a complete understanding of the fluid flow behavior inside the cabinet, the influence of the door opening was analyzed.\u0000 Results of the CFD simulations allowed to achieve a detailed mapping of the cooling process inside the equipment. Generally, stabilizing the interior temperature for an empty cabinet is rapidly achieved with minimal heat losses. The inclusion of products that are at a higher temperature than the cooling air creates a zone of high thermal inertia and makes the temperature stabilization a longer process. Even though specific equipment is used, the results provide standard information on the phenomena occurring inside the cabinet and contribute to the industry and academic society to understand and improve industrial products and obtain more information that is very reduced in the literature.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116740683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Droplet Dynamics in PEM Fuel Cell Flow Channels","authors":"M. Mortazavi, Vedang Chauhan, T. Pedley, Brian M. Whinery","doi":"10.1115/imece2021-71972","DOIUrl":"https://doi.org/10.1115/imece2021-71972","url":null,"abstract":"\u0000 During the operation of proton exchange membrane (PEM) fuel cells, water is produced in the cathode side. The produced water passes through the porous structure of the electrode and emerges from the surface of the gas diffusion layer (GDL) within the flow channel. The emerged droplet is constantly fed through liquid columns which are formed underneath the droplet within the GDL. This study focuses on dynamics of growing droplets on the surface of the GDL which are exposed to shear gas flow. High-speed imaging was implemented to visualize droplet dynamics from emergence to detachment as the pressure drop across the droplet was measured simultaneously. Images were processed with MATLAB code which was developed in-house to obtain droplet lateral area and the location of the droplet centroid. Results clearly demonstrated that droplets underwent an oscillatory mode for both superficial gas velocities tested in this study. While the oscillatory motion was observed both in horizontal (i.e. stream-wise direction) and vertical directions, the amplitude of the oscillation was greater in the horizontal direction. In addition, the oscillation amplitude was observed to increase with droplet size and reached the maximum value upon droplet detachment. For a superficial gas velocity of 10.76 m/s, the oscillation amplitude upon detachment was as high as around 0.16 mm in x direction while the corresponding oscillation in y direction was around 0.06 mm. Study of contact angles revealed that while the advancing and receding contact angles for the superficial gas velocity of 4.17 m/s are higher than angles for the superficial gas velocity of 10.76 m/s, the contact angle hysteresis for both velocities were almost identical upon detachment.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126936520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computation of Three-Dimensional Mixed Convection in a Horizontal Rectangular Duct","authors":"Abimbola Oluwade, E. Glakpe","doi":"10.1115/imece2021-71938","DOIUrl":"https://doi.org/10.1115/imece2021-71938","url":null,"abstract":"\u0000 Numerical investigation of mixed convection heat transfer in a three-dimensional, horizontal, rectangular duct has been carried out using COMSOL Multiphysics® simulation software. The bottom wall of the duct is subjected to a uniform heat flux condition, while the top and sidewalls are adiabatic. Uniform flow of water at 23°C (Pr = 6.5) is assumed to enter the duct of aspect ratio in the range of 1 ≤ A ≤ 10. Numerical computations are carried out for Re = 500 and modified Grashof number (Gr*) in the range of 2.5 × 105 ≤ Gr* ≤ 6.5 × 106. Results of the flow structure, local averaged friction factor (f), and local averaged Nusselt number (Nu) at the bottom of the duct for Re = 500, A = 2, and Gr* = 2.5 × 106 are compared with those from Incropera et al. [11]. Additionally, Nu values are also obtained for increased values of A and Gr* and compared with results from Incropera et al. [11]. Alongside incompressible flow with Boussinesq approximation, results are obtained for the weakly compressible form of the body force terms available in COMSOL Multiphysics®. Results show good agreement with published results in the literature, and the two results from the two approaches to approximating the body force terms are largely similar except at high Gr*. Additionally, a maximum heat transfer enhancement by buoyancy of ≈ 310% was found.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128269261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}