scholarly journals Low Reynolds Number Rotor Blade Aerodynamic Analysis

2019 ◽  
Vol 252 ◽  
pp. 04006
Author(s):  
Tytus Tulwin
Keyword(s):  
Reynolds Number ◽  
Energy Use ◽  
Low Reynolds Number ◽  
Hydrocarbon Fuel ◽  
High Energy ◽  
Tip Vortex ◽  
Induced Drag ◽  
Energy Consumption Reduction ◽  
Power Loading ◽  
Low Reynolds

Maintaining a steady hover flight in a rotorcraft usually requires high energy input. The aim of the paper is to prove that it is possible to vastly reduce energy use in a rotorcraft by reducing the disc loading. The energy consumption reduction is especially important in electric rotorcraft, where the energy source is characterized by low energy density when compared to the hydrocarbon fuel in ICE rotorcraft. The paper presents results of CFD simulations on low Reynolds Number operating rotors. For low RE rotors tip vortex induced drag is highly affecting the rotor’s Figure of Merit, thus reducing rotor performance. Even though FM is reduced, the low RE setup is still beneficial in terms of reduced Power Loading, the main factor responsible for hover endurance.

Cycloidal Rotor-Blade Tip-Vortex Analysis at Low Reynolds Number

AIAA Journal ◽  
2020 ◽  
Vol 58 (6) ◽  
pp. 2560-2570
Author(s):  
James W. McElreath ◽  
Moble Benedict ◽  
Nathan Tichenor
Keyword(s):  
Reynolds Number ◽  
Rotor Blade ◽  
Low Reynolds Number ◽  
Tip Vortex ◽  
Blade Tip ◽  
Low Reynolds

Correction of low-Reynolds number turbulence model to hydrocarbon fuel at supercritical pressure

2018 ◽  
Vol 77 ◽  
pp. 156-167 ◽  
Author(s):  
Zhi Tao ◽  
Zeyuan Cheng ◽  
Jianqin Zhu ◽  
Xizhuo Hu ◽  
Longyun Wang
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Low Reynolds Number ◽  
Hydrocarbon Fuel ◽  
Supercritical Pressure ◽  
Low Reynolds

Membrane Wing-Based Micro Air Vehicles

2005 ◽  
Vol 58 (4) ◽  
pp. 283-301 ◽  
Author(s):  
Wei Shyy ◽  
Peter Ifju ◽  
Dragos Viieru
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Optimization Technique ◽  
Micro Air Vehicles ◽  
Flight Speed ◽  
Tip Vortex ◽  
Flexible Wing ◽  
Membrane Wing ◽  
Low Reynolds ◽  
Air Vehicles

Micro air vehicles (MAVs) with a wingspan of 15cm or shorter, and flight speed around 10m∕s have attracted substantial interest in recent years. There are several prominent features of MAV flight: (i) low Reynolds number (104-105), resulting in degraded aerodynamic performance, (ii) small physical dimensions, resulting in certain favorable scaling characteristics including structural strength, reduced stall speed, and impact tolerance, and (iii) low flight speed, resulting in order one effect of the flight environment and intrinsically unsteady flight characteristics. Flexible wings utilizing membrane materials are employed by natural flyers such as bats and insects. Compared to a rigid wing, a membrane wing can better adapt to the stall and has the potential for morphing to achieve enhanced agility and storage consideration. We will discuss the aerodynamics of both rigid and membrane wings under the MAV flight condition. To understand membrane wing performance, the fluid and structure interaction is of critical importance. Flow structures associated with the low Reynolds number and low aspect ratio wing, such as pressure distribution, separation bubble, and tip vortex, as well as structural dynamics in response to the surrounding flow field are discussed. Based on the computational capabilities for treating moving boundary problems, an automated wing shape optimization technique is also developed. Salient features of the flexible-wing-based MAV, including the vehicle concept, flexible wing design, novel fabrication methods, aerodynamic assessment, and flight data analysis are highlighted.

3D Numerical Analysis of Heat Transfer in a Low Reynolds Number Microturbine Cascade

2012 ◽  
Author(s):  
M. Omri ◽  
S. Moreau ◽  
L. G. Fréchette
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Waste Heat ◽  
Low Reynolds Number ◽  
Three Dimensional ◽  
Suction Side ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Distributed Power Generation ◽  
Low Reynolds

This paper presents the conjugate heat transfer in a submillimeter scale microturbine characterized by laminar yet highly three-dimensional flows. Such a miniature turbine is part of a MEMS (microelectromechanical system) power plant-on-a-chip currently under development for distributed power generation from waste heat. Adiabatic subsonic flows in the turbine have previously been studied numerically and are characterized by low Reynolds number laminar flow (Re < 2500) but with complex vortical structures. The present work addresses the influence of these flow structures on heat transfer, including the effect of the horseshoe and tip vortices. Calculations were done for tip clearance gaps equal to 0%, 5% and 10% blade height. Three different scenarios were considered: adiabatic walls, the hub and casing temperature of 573K or the hub at 573K and the casing at 450K, for incoming flow at 600K. The heat transfer is more variable in the suction side since dominant vortices are adjacent to this blade side. The heat flux even changes its sign where the vortices begin to separate from the suction side, indicating that gas cooled in the hub and casing boundary layers is transported on the blades by the horseshoe vortices. The tip vortex prevents the top passage vortex from interacting with the suction side, which eliminates the negative heat transfer in this region. Due to the dominant vortices, the Nusselt number is found to be a function of the thermal boundary conditions and cannot be predicted with traditional boundary layer correlations.

scholarly journals Measurement of particle accelerations in fully developed turbulence

2002 ◽  
Vol 469 ◽  
pp. 121-160 ◽  
Author(s):  
GREG A. VOTH ◽  
A. LA PORTA ◽  
ALICE M. CRAWFORD ◽  
JIM ALEXANDER ◽  
EBERHARD BODENSCHATZ
Keyword(s):  
Reynolds Number ◽  
Particle Physics ◽  
Large Scale ◽  
Low Reynolds Number ◽  
High Energy ◽  
Frame Rate ◽  
High Energy Particle ◽  
Particle Trajectories ◽  
Low Reynolds ◽  
Acceleration Component

We use silicon strip detectors (originally developed for the CLEO III high-energy particle physics experiment) to measure fluid particle trajectories in turbulence with temporal resolution of up to 70000 frames per second. This high frame rate allows the Kolmogorov time scale of a turbulent water flow to be fully resolved for 140 [ges ] Rλ [ges ] 970. Particle trajectories exhibiting accelerations up to 16000 m s −2 (40 times the r.m.s. value) are routinely observed. The probability density function of the acceleration is found to have Reynolds-number-dependent stretched exponential tails. The moments of the acceleration distribution are calculated. The scaling of the acceleration component variance with the energy dissipation is found to be consistent with the results for low-Reynolds-number direct numerical simulations, and with the K41-based Heisenberg–Yaglom prediction for Rλ [ges ] 500. The acceleration flatness is found to increase with Reynolds number, and to exceed 60 at Rλ = 970. The coupling of the acceleration to the large-scale anisotropy is found to be large at low Reynolds number and to decrease as the Reynolds number increases, but to persist at all Reynolds numbers measured. The dependence of the acceleration variance on the size and density of the tracer particles is measured. The autocorrelation function of an acceleration component is measured, and is found to scale with the Kolmogorov time τη.

Experimental Investigation on Blunt-Edged UTM Delta Wing VFE-2 Configurations at Low Reynolds Number

2018 ◽  
Vol 12 (3) ◽  
pp. 255
Author(s):  
Muhammad Zal Aminullah Daman Huri ◽  
Shabudin Bin Mat ◽  
Mazuriah Said ◽  
Shuhaimi Mansor ◽  
Md. Nizam Dahalan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Delta Wing ◽  
Low Reynolds Number ◽  
Low Reynolds
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