Vortex and the Balance between Vorticity and Strain Rate

Kolář, V.; Šístek, Jakub

doi:10.1155/2019/1321480

Cited by 8 publications

(3 citation statements)

References 32 publications

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“…In simple terms, the criterion identifies as vortices those regions where vorticity magnitude is larger than the strain-rate magnitude, or more precisely, where their difference is positive. Among the main advantages of the Q-criterion are its simplicity and straightforward application [17]. In this paper, NACA 0012 airfoil is used for simulation and optimization purposes.…”

Section: B Post-processingmentioning

confidence: 99%

Aerodynamic Simulation and Optimization of Micro Aerial Vehicle Rotor Airfoil at Low Reynolds Number

Nepal

Zhao

Wang

et al. 2023

ARME

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This paper describes the aerodynamic simulation and optimization of NACA 0012 airfoil at a low Reynolds number using unsteady Reynolds-averaged Navier-Stokes (URANS) and Spalart–Allmaras turbulence model in Ansys Fluent. The purpose of this paper is to simulate and optimize the airfoil to get better aerodynamic performances at low Reynolds numbers. The Parsec method was selected for the optimization of the NACA 0012 airfoil. Both of these airfoils are simulated using CFD Fluent between 0 to 13-degree angle of attack at a low Reynolds number of 200000. To simulate the airfoil, mesh generation is crucial so an O-grid structured mesh is created. After the simulation, several aerodynamic performances are compared between the airfoils, such as lift coefficient, drag coefficient, pressure coefficient, and lift-to-drag ratio. And the calculated results from Xfoil are taken as references. Between NACA 0012 and optimized NACA 0012, the optimized airfoil showed better aerodynamic performances than the normal one, which was the goal of this paper. Later on, the different flow field variables, such as density, temperature, pressure, and vorticity magnitude were analyzed and compared. Both the airfoils at a different angle of attack were analyzed for these functions, like 7°, 11°, and 20° AOA. During the analytical process, Q-criterion appears to be a very important method of vortex identification in the flow field. With this analysis, we came to know, that as the angle of attack increases the adverse pressure gradient also increases, which creates a big reverse flow.

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Section: B Post-processingmentioning

confidence: 99%

Aerodynamic Simulation and Optimization of Micro Aerial Vehicle Rotor Airfoil at Low Reynolds Number

Nepal

Zhao

Wang

et al. 2023

ARME

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“…To visualize the wake flow from each case, Q-criterion was calculated and the iso-surface of it was generated in ANSYS Fluent. Q-criterion (𝑄) is one of several methods to identify vortex in the wake flow by way of calculating the difference between the vorticity magnitude and the strain-rate magnitude within the flow [29,30]. Positive values of Q-criterion indicate the vortex regions in the wake flow, and the value used for the iso-surface to visualize different cases of flow will differ depending on the type of flow that is being analyzed [6,7,10,[29][30][31].…”

Section: A Near-field Wake Flow Simulationmentioning

confidence: 99%

“…Q-criterion (𝑄) is one of several methods to identify vortex in the wake flow by way of calculating the difference between the vorticity magnitude and the strain-rate magnitude within the flow [29,30]. Positive values of Q-criterion indicate the vortex regions in the wake flow, and the value used for the iso-surface to visualize different cases of flow will differ depending on the type of flow that is being analyzed [6,7,10,[29][30][31]. Figure 1 shows the flow visualization (iso-surface 𝑄 = 20) from the near-field flow simulation using different quadrotor propellers and forward flight conditions.…”

Section: A Near-field Wake Flow Simulationmentioning

confidence: 99%

A Study on Circulation Strength Decay Over Time of Quadrotor Wake Using Large Eddy Simulation

Nathanael

Wang

Low

2022

AIAA SCITECH 2022 Forum

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As the use of multi-rotors is becoming common, understanding how the wake vortices develop and decay from a multi-rotor is important to reduce the effect of wake vortices on other multi-rotors and ensure their safety during operation by applying a wake separation minima. This paper proposes a method of flow simulation in ANSYS Fluent to study the decay of wake vortices from quadrotor propellers as the vortices evolve over distance and time. First, the near-field wake flow from the quadrotor propellers was simulated using Reynolds-Averaged Navier-Stokes (RANS) turbulence model. The velocity profile in the quadrotor frame of reference was then extracted to be applied for a flow simulation using Large Eddy Simulation (LES). The circulation strength as a function of distance could then be calculated, but it was limited by the length of the computational grid due to the wake flow being seen from the quadrotor frame of reference. To change into the stationary frame of reference, the interpolation data from the first stage LES was exported and modified by subtracting the freestream velocity from the velocity component in the freestream direction. The modified interpolation data was then used for the second stage LES, and the circulation strength in terms of time could be calculated from the resulting wake flow. Three cases of flow simulation are presented in this paper: first using 380-mm-diameter propellers based on the SUI Endurance quadrotor propellers with forward flight speed of 6 m/s, second using the 380-mm-diameter propellers with 12 m/s speed, and third using 240-mm-diameter propellers (similar to the propellers of DJI Phantom quadrotor) with 12 m/s speed. Findings regarding the decay of wake vortex from multi-rotor vehicles will help in determining the safe separation distance required to mitigate the hazards due to wake vortex encounters and ensure the safety of multi-rotor vehicles.

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Comparison of Vortex Identification Methods Based on the Liutex Decomposition and Application in a Compressor Cascade

Zhong

Tang

Liu

2023

Springer Proceedings in Physics

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Vortex and the Balance between Vorticity and Strain Rate

Cited by 8 publications

References 32 publications

Aerodynamic Simulation and Optimization of Micro Aerial Vehicle Rotor Airfoil at Low Reynolds Number

Aerodynamic Simulation and Optimization of Micro Aerial Vehicle Rotor Airfoil at Low Reynolds Number

A Study on Circulation Strength Decay Over Time of Quadrotor Wake Using Large Eddy Simulation

Comparison of Vortex Identification Methods Based on the Liutex Decomposition and Application in a Compressor Cascade

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