scholarly journals Structure and stability of Joukowski's rotor wake model

2021 ◽  
Vol 911 ◽  
Author(s):  
E. Durán Venegas ◽  
P. Rieu ◽  
S. Le Dizès
Keyword(s):  
Rotor Wake ◽  
Structure And Stability ◽  
Wake Model

Abstract

Three Dimensional Characteristics of Turbulent Wakes Behind Rotors of Axial Flow Turbomachinery

1976 ◽  
Vol 98 (2) ◽  
pp. 218-227 ◽  
Author(s):  
R. Raj ◽  
B. Lakshminarayana
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Decay Rates ◽  
Experimental Investigations ◽  
Mean Velocity ◽  
Rotor Wake ◽  
Turbulent Wakes ◽  
Stress Maximum ◽  
Wake Model ◽  
Rotor Profiles

Analytical and experimental investigations of the characteristics of three-dimensional turbulent wakes downstream of a turbomachinery rotor are reported in this paper. An approximate quasi-three-dimensional turbulent wake model for turbomachinery rotor is developed and compared with the cascade and isolated airfoil wake models. The rotor wake model is capable of predicting the decay of mean component of radial and streamwise velocities as a function of rotor geometry, speed of rotation, and the turbulence properties of the flow field. A rotation parameter based on similarity analysis is derived. The velocity profiles in both the radial and cylindrical planes are coupled together. Measurement of mean velocities (U¯n, U¯s, U¯r), turbulent intensities and stresses (un2¯, us2¯, ur2¯, usun¯, unur¯, usur¯) is carried out using a triple sensor hot wire probe in a stationary system at various axial and radial locations downstream of the rotor. Profiles of mean and turbulent quantities are obtained. Semi-theoretical expressions for the decay rates of the defect in mean velocity, turbulence intensity, and Reynolds stress (maximum values) with distance downstream of the rotor are derived. The experimental data on the rotor wake are compared with that of an isolated airfoil and cascade of airfoils. The investigation suggests that rotor wake decays much faster than the cascade or an isolated airfoil wake.

Numerical Analysis of Rotor/Propeller Aerodynamic Interactions on a High-Speed Compound Helicopter

2021 ◽  
Author(s):  
Ronan Boisard
Keyword(s):  
High Speed ◽  
Strong Interactions ◽  
Main Rotor ◽  
Rotor Wake ◽  
Precise Control ◽  
High Speeds ◽  
Computational Fluid Dynamics Cfd ◽  
Compound Helicopter ◽  
Wake Model ◽  
Free Wake

In the context of the development of high-speed compound helicopters, the main rotor may not be an efficient propulsive device at high speeds and adding a propulsive propeller is a means to enable higher speed. On such configuration, at low speed, the propellers are in strong interactions with the main rotor wake which affects their performance and aircraft maneuverability. The present work numerically investigates the aerodynamics of the rotor/propeller interaction on rotorcraft similar to the Racer from Airbus Helicopters. Through the comparison of two different levels of fidelity for three different advance ratios, it is shown that at high advance ratio, a simple free wake model is suitable to give most of the interaction effects, while in hover, a full computational fluid dynamics (CFD) unsteady computation is necessary to better capture all the unsteadiness of the interaction. The detailed analysis of CFD results also outlines the different behaviors of the propeller when it is fully inside the rotor wake or out of it, and therefore the need for a precise control of the rotorcraft in the transition between hover to fast forward flight.

The Inverse Vortex Wake Model: A Measurement Analysis Tool

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Wouter Haans ◽  
Gijs van Kuik ◽  
Gerard van Bussel
Keyword(s):  
Wind Tunnel ◽  
Analysis Tool ◽  
Vortex Wake ◽  
Flow Conditions ◽  
Rotor Wake ◽  
Rotor Aerodynamics ◽  
Measurement Analysis ◽  
Wake Model ◽  
Induced Velocity ◽  
Blade Loads

To reduce the level of uncertainty associated with current rotor aerodynamics codes, improved understanding of rotor aerodynamics is required. Wind tunnel measurements on model rotors contribute to advancing our knowledge on rotor aerodynamics. The combined recording of blade loads and rotor wake is desired, because of the coupled blade and wake aerodynamics. In general, however, the small size of model rotors prohibits detailed blade load measurements; only the rotor wake is recorded. To estimate the experimental blade flow conditions, a measurement analysis tool is developed: the inverse vortex wake model. The rotor wake is approximated by a lifting line model, using rotor wake measurements to reconstruct the vortex wake. Conservation of circulation, combined with the Biot–Savart law, allows the induced velocity to be expressed in terms of the bound circulation. The unknown bound circulation can be solved for, since the velocity is known from rotor wake measurements. The inverse vortex wake model is subsequently applied to measurements on the near wake of a model rotor subject to both axial and yawed flow conditions, performed at a TUDelft open jet wind tunnel. The inverse vortex wake model estimates the unsteady experimental blade flow conditions and loads that otherwise would have remained obscured.

A three-dimensional wake model for low earth orbit

1983 ◽  
Author(s):  
I. KATZ ◽  
D. COOKE ◽  
D. PARKS ◽  
M. MANDELL ◽  
A. RUBIN
Keyword(s):  
Three Dimensional ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Wake Model

Polyplex: A Promising Gene Delivery System

2019 ◽  
Vol 12 (6) ◽  
pp. 4681-4686
Author(s):  
Rohan Aggarwal ◽  
Monika Targhotra ◽  
Bhumika Kumar ◽  
P.K Sahoo ◽  
Meenakshi K Chauhan
Keyword(s):  
Gene Transfer ◽  
Gene Delivery ◽  
Delivery System ◽  
Viral Vectors ◽  
Gene Delivery System ◽  
Cationic Polymers ◽  
Therapeutic Application ◽  
Promising Alternative ◽  
Structure And Stability ◽  
The Past

In the past few years gene delivery system has gained a huge attention owing to its proved efficacy in several diseases especially in those caused by genetic and/oroncological malfunctioning. The effective gene delivery mainly depends on the carrier molecules that can ensure the safe and specific delivery of the nucleic acidmolecules. Viral vectors have been used for a longer period as the gene transfer vehicle. However, these viral vectors have potential immunological disadvantages that made them less preferred. Recently, non-viral vectors such as polyplexes have emerged as a promising alternative for viral vectors. Polyplexes are formed by conjugating a polymer with DNA and in maximum cases the cationic polymers are preferred over others. The structure and stability of the polyplexes depends on various factors. The ability of the polymer to condense the DNA mainly dictates the efficiency of the polyplex mediated transfection. In this review we are going to provide a framework for the synthesis and design of the polyplexes along with the structure and stability of the complexes pertaining to mechanism of action, characterization and therapeutic application, including polyethyleneimine mediated cytotoxicity as well as newer strategies for the generation of better polyplexes.

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