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Author: A. Krothapalli
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
An experimental investigation was carried out to study the mixing characteristics of a moderate aspect ratio rectangular free and confined jet; and free and confined multiple jet. The main parameters were the primary jet pressure ratio (stagnation pressure/ambient pressure) and the ejector mixing duct to width ratio. The pressure ratio varied from 1.5 to 5; the mixing duct to width ratio varied from 8 to 24, which is equivalent to the cross sectional area ratio from 11 to 34. It is found that an underexpanded jet inside a duct generates intense discrete tones (screech tones) similar to a free underexpanded jet. For a given pressure ratio, the variation of the dominant tone with duct widths shows staging behavior, and the frequency varies continuously with duct width in each stage. Similarly, for a given duct width, the variation of the dominant discrete frequency with pressure ratio shows staging behavior. It is found that enhanced mixing and improved performance of the ejector was related to the strouhal number of the ejector screech tone. For all the duct widths tested, it is found that when the screech tone strouhal number lies within the range 0.1 0.15, the primary jet spreading is increased and the ejector flow is better mixed at the exit.
Author: A. Krothapalli
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
An experimental investigation was carried out to study the mixing characteristics of a moderate aspect ratio rectangular free and confined jet; and free and confined multiple jet. The main parameters were the primary jet pressure ratio (stagnation pressure/ambient pressure) and the ejector mixing duct to width ratio. The pressure ratio varied from 1.5 to 5; the mixing duct to width ratio varied from 8 to 24, which is equivalent to the cross sectional area ratio from 11 to 34. It is found that an underexpanded jet inside a duct generates intense discrete tones (screech tones) similar to a free underexpanded jet. For a given pressure ratio, the variation of the dominant tone with duct widths shows staging behavior, and the frequency varies continuously with duct width in each stage. Similarly, for a given duct width, the variation of the dominant discrete frequency with pressure ratio shows staging behavior. It is found that enhanced mixing and improved performance of the ejector was related to the strouhal number of the ejector screech tone. For all the duct widths tested, it is found that when the screech tone strouhal number lies within the range 0.1 0.15, the primary jet spreading is increased and the ejector flow is better mixed at the exit.
Author:
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 300
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Book Description
Some experimental and theoretical studies have been made of axisymmetric free jets exhausting from sonic and supersonic nozzles into still air and into supersonic streams with a view toward problems associated with propulsive jets and the investigation of these problems. For jets exhausting into still air, consideration is given to the effects of jet Mach number, nozzle divergence angle, and jet static-pressure ratio upon jet structure, jet wavelength, and the shape and curvature of the jet boundary. Studies of the effects of the ratio of specific heats of the jets are included as are observations pertaining to jet noise and jet simulation. For jets exhausting into supersonic streams, an attempt has been made to present primarily theoretical curves of the type that may be useful in evaluating certain jet interference effects and in formulating experimental studies. The primary variables considered are jet Mach number, free-stream Mach number, jet static-pressure ratio, ratio of specific heats of the jet, nozzle exit angle, and boattail angle. The simulation problem and the case of a hypothetical hypersonic vehicle are examined. A few experimental observations are included.
Author: A. Krothapalli
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Book Description
A continuing series of experiments is being carried out to study the basic fluid mechanical properties of single and multiple rectangular jets in a free and confined environment. This work was motivated by the use of these jets in an augmentor wing considered by NASA Ames Research Center.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
Author: Yasuhiro Kamotani
Publisher:
ISBN:
Category : Eddies
Languages : en
Pages : 84
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Book Description
Author: Suyambazhahan S.
Publisher: LAP Lambert Academic Publishing
ISBN: 9783843380027
Category :
Languages : en
Pages : 60
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Book Description
This book deals with the numerical and experimental study of oscillations in laminar free and impinging jets. A finite volume algorithm based on non-orthogonal cells has been used to solve the transient, incompressible Navier-Stokes equations for two dimensional flow. The code has been employed for the prediction of flow and thermal oscillations in isothermal and non-isothermal jets. For free jets, the effects of parameters such as Reynolds number, inlet temperature and jet orientation on oscillations have been studied. For impinging jet flow, the effects of stand-off distance, Reynolds number and inlet temperature on mean flow as well as jet oscillations have been studied.
Author: G. Fabris
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
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Book Description
The study deals with the transfer of kinetic energy from an array of primary jets to a surrounding secondary stream. It explores the basic features of such flows and examines to what extent the results of single jet research may be applied to multiple jet configurations. It presents an analytical technique for estimating the performance of multiple jets and examines in a special multiple - jet test facility the validity of the assumptions used in the analysis. (Author Modified Abstract).
Author: Zhimin Hu
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 518
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Book Description
Author: J. Zhu
Publisher:
ISBN:
Category :
Languages : en
Pages : 30
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Book Description
A numerical investigation is reported of turbulent incompressible jets confined in two ducts, one cylindrical and the other conical with a 5 degree divergence. In each case, three Craya-Curtet numbers are considered which correspond, respectively, to flow situations with no moderate and strong recirculation. Turbulence closure is achieved by using the k-epsilon model and a recently proposed realizable Reynolds stress algebraic equation model that relates the Reynolds stresses explicitly to the quadratic terms of the mean velocity gradients and ensures the positiveness of each component of the turbulent kinetic energy. Calculations are carried out with a finite-volume procedure using boundary-fitted curvilinear coordinates. A second-order accurate, bounded convection scheme and sufficiently fine grids are used to prevent the solutions from being contaminated by numerical diffusion. The calculated results are compared extensively with the available experimental data. It is shown that the numerical methods presented are capable of capturing the essential flow features observed in the experiments and that the realizable Reynolds stress algebraic equation model performs much better than the k-epsilon model for this class of flows of great practical importance.
Author: Dennis Earl Stowell
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 278
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Book Description
