Large eddy simulations of ventilated micro-hydrokinetic turbine and pump-turbines

Large eddy simulations of ventilated hydrokinetic turbine and pump-turbine are conducted. The mathematical modeling of oxygen dissolution and the flow model employed were validated by comparing predicted dissolved oxygen concentration against reported experimental measurements. A parametric study is performed to investigate the influence of interfacial forces, surface tension and bubble breakage and coalescence terms. It is demonstrated that aeration via hydrokinetic turbines can be used to improve the dissolved oxygen level in rivers for better water quality. It is also shown that aeration can effectively be achieved via the pump-turbine system to provide the desired dissolved oxygen level for the microorganisms’ growth during the wastewater treatment process. Air injection is applied to the wake region of each unit. The influence of aeration on the turbine performance, flow induced vibration and oxygen dissolution characteristics are investigated. The numerical predictions reveal that the aeration can be utilized in both hydro systems without experiencing a significant penalty in power generations. Aeration significantly reduces the flow induced vibration in the pump turbine system. The pressure pulsation on the draft tube surface of the pump-turbine is reduced significantly with both central and peripheral aeration. In hydrokinetic turbine, the variation in the standard deviation of power, which is related to the vibration of the turbine unit, is strongly dependent on the turbine operating conditions. Draft tube aeration provided 30% greater amount of dissolved oxygen and 3.2 times higher dissolution efficiency inside the draft tube as compared to the central aeration. The mathematical approaches and the numerical methods employed here can be used to design and optimize the aeration process in these systems

Steady State and Transient Computational Study of Multiple Hydrokinetic Turbines

Computational fluid dynamics (CFD) simulations have been conducted for different configurations of pre-designed multiple hydrokinetic turbines. The turbines are modeled physically within the fluid domain instead of low fidelity actuator lines or actuator disk modeling approaches. The turbulence model, k-ω Shear Stress Transport (SST) was employed to resolve turbulent flow field. The primary focus of this study is to investigate transient behavior of multiple turbines and providing solutions to enhance downstream turbine performance in close proximity to the upstream turbine wake. The wake interaction behind the upstream turbine reduces downstream turbine performance with inline configurations being the most severe cases. One of the many suggested solutions is staggering downstream units beyond the wake region. Other solutions for an inline array: increasing the longitudinal distance between units and modifying downstream turbine rotation speed to move turbine operation point to the best efficiency point.The CFD simulations revealed that the upstream turbine power generation is nearly the same with the single unit power generation for each multiple turbine arrangement. The downstream turbine relative power obtained was 0.18 for the unit placed inline and 0.98 when it was placed outside the wake region. For inline configurations, increasing the stream-wise spacing between the units from 6Dt to 10Dt improved relative power from 0.16 to 0.60, while reducing the rotation speed from 150 rpm to 100 rpm resulted relative power increment from 0.24 to 0.55

Designing a Rear Wing for Binghamton\u27s Formula Race Car: From Small-Scale Simulations and Experiments to Full-Scale Manufacturing

Binghamton\u27s Formula Society of Automotive Engineers (FSAE) designed an aerodynamically efficient rear wing with three airfoils for their new electric vehicle (EV) to improve lap time. They used an integral model, JavaFoil, to determine the size and configuration of each airfoil. Over 4,000 simulations were conducted to determine the optimal spacing and angle of attack for each airfoil to achieve the best downforce. The results were confirmed through computational fluid dynamics (CFD) simulations and experiments at the AEROLAB Wind Tunnel. The final configuration was manufactured using a manual wet layup technique for epoxy resin and carbon fiber. The rear wing assembly will be installed on the 2023 FSAE EV vehicle, which will compete in June 2023 at the Michigan International Speedway. The findings and insights gained from this project will not only assist future aerodynamics teams at Binghamton Motorsports but will also benefit other FSAE teams.https://orb.binghamton.edu/research_days_posters_2023/1033/thumbnail.jp

Vortex Identification in Turbulent Flows Past Plates using Lagrangian Method

Vortex identifications in turbulent flows past arrays of tandem plates are performed by employing the velocity field obtained by high fidelity large eddy simulations (LES). Lagrangian coherent structures (LCSs) are extracted to examine the evolution and the nonlinear interaction of vortices and to characterize the spatial and temporal characteristics of the flow. LCSs identification method is based on the Finite-Time Lyapunov Exponent (FTLE) which is evaluated using the instantaneous velocity data. The simulations are performed in three-dimensional geometries to understand the physics of fluid motion and the vortex dynamics in the vicinity of plates and surfaces at Reynolds number of 50,000. The instantaneous vorticity fields, Eulerian Q-criterion and LCSs are presented to interpret and understand complex turbulent flow structures. The three-dimensional FTLE fields provide valuable information about the vortex generation, spatial location, evolution, shedding, decaying and dissipation of vortices. It is demonstrated here that FTLE can be used together with Eulerian vortex identifiers to characterize the turbulent flow field effectively.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author