Compressible plane turbulent wakes under pressure gradients evolving in a constant area section

2020 ◽  
Vol 892 ◽  
Author(s):  
Chitrarth Lav ◽  
Jimmy Philip ◽  
Richard D. Sandberg
Keyword(s):  
Pressure Gradients ◽  
Turbulent Wakes ◽  
Constant Area ◽  
Image Position ◽  
Area Section

Increased Turbulent Jet Mixing Rates Obtained by Self-Excited Acoustic Oscillations

1977 ◽  
Vol 99 (3) ◽  
pp. 520-525 ◽  
Author(s):  
W. G. Hill ◽  
P. R. Greene
Keyword(s):  
Large Scale ◽  
Exit Section ◽  
Acoustic Oscillations ◽  
Convergent Nozzle ◽  
Jet Mixing ◽  
New Device ◽  
Constant Area ◽  
Wide Range ◽  
Mixing Rates ◽  
Area Section

A new device, capable of greatly increasing subsonic jet mixing rates, has been discovered. This device, which we have named the “whistler nozzle,” consists of a convergent nozzle section, a constant area section, and a step change to an exit section with a larger constant area. The exit section excites a standing acoustic wave in the constant area section, in a way similar to the action of an organ pipe. The result of this resonance is a loud pure tone and a greatly increased rate of jet mixing. The increased mixing rates appear related to the acoustically stimulated vortex shedding character (large scale structure or superturbulence) observed by Crow and Champagne [1] in their pioneering study of jets excited by a loudspeaker, and others utilizing upstream valves and pistons, except that the whistler nozzle is self-excited. The standing wave and the resulting increased mixing rates occur for a wide range of exit plane configurations and jet parameters.

Two-dimensional turbulent wakes

1967 ◽  
Vol 30 (3) ◽  
pp. 547-560 ◽  
Author(s):  
Ian S. Gartshore
Keyword(s):  
Shear Stress ◽  
Stress Reduction ◽  
Shear Stresses ◽  
Pressure Gradients ◽  
Two Dimensional ◽  
Stress Distributions ◽  
Mean Velocity ◽  
Lower Shear ◽  
Turbulent Wakes ◽  
Velocity Scale

The equations of mean motion indicate that two-dimensional turbulent wakes, when subjected to appropriately tailored adverse pressure gradients, can be self-preserving. An experimental examination of two nearly self-preserving wakes is reported here. Mean velocity, longitudinal and lateral turbulence intensity, inter-mittency and shear stress distributions have been measured and are compared with Townsend's data from the small-deficit undistorted wake. In comparison with the undistorted case, the present wakes have slightly lower turbulent intensities and significantly lower shear stresses, all quantities being non-dimensionalized by a local velocity scale taken as the maximum mean velocity deficit. A consideration of the reasons for the shear stress reduction leads to an expression from which the shear stresses in any symmetrical free equilibrium shear flow can be found. This relationship is used to calculate the rate of growth in the measured wakes, with reasonable success.

Numerical Investigation of Geometric Factors for Design of High Performance Air-Jet Pumps Using in Vehicle-Mounted Vacuum Toilet

2011 ◽  
Vol 268-270 ◽  
pp. 46-50
Author(s):  
Fei Gao ◽  
Jing Xuan Zhou ◽  
Min Li
Keyword(s):  
High Performance ◽  
Operating Conditions ◽  
Cfd Model ◽  
Jet Pump ◽  
Air Jet ◽  
Geometric Factors ◽  
Constant Area ◽  
Jet Pumps ◽  
Computational Fluid Dynamics Cfd ◽  
Area Section

Air-jet pump as the pneumatic source of a vehicle-mounted vacuum toilet provides the vacuum to pump the fecal sewage out of toilet bowl via the compressed air passing through the pump under certain pressure. In this study, Computational Fluid Dynamics (CFD) technique is employed to investigate the effects of three important air-jet pump geometry parameters: the primary Nozzle Exit Position (NXP), the constant-area section length (L1) and the diffuser diverging angle (θ), on its performance. A CFD model is firstly established according to 1D analytical method, and then used to create 135 different air-jet pump geometries and tested under different operating conditions. The significance of this study is that these findings can be used to guide the adjustment of NXP, L1 and θ to obtain the best air-jet pump performance when the operating conditions are different.

A NEW 1D MODEL FOR SUPERSONIC EJECTOR PERFORMANCE EVALUATION AT CRITICAL AND SUB-CRITICAL OPERATIONAL MODES

2014 ◽  
Vol 22 (01) ◽  
pp. 1430001 ◽  
Author(s):  
A. MAGHSOODI ◽  
H. AHMADIKIA ◽  
M. DADVAR
Keyword(s):  
Constant Pressure ◽  
Critical Mode ◽  
Entrainment Ratio ◽  
Supersonic Ejector ◽  
Operation Conditions ◽  
Constant Area ◽  
1D Model ◽  
Mass Flow Rates ◽  
Operational Modes ◽  
Area Section

A new 1D model is proposed to predict ejector performance at critical and sub-critical operational modes, while most previous 1D models have predicted ejector performance only at critical mode. Constant pressure mixing is assumed to occur inside the constant area section of the ejector at both operational modes. Experimental data from different ejector geometries and various operation conditions reported earlier are used to verify the effectiveness of the new model. The model has a good performance in predicting the mass flow rates and the entrainment ratio, a useful tool for predicting ejector performance within larger refrigeration cycle models.

Investigations of the Effect of Constant-Area Section on Thermal Choking in a Dual-Mode Scramjet Combustor

2016 ◽  
Vol 29 (5) ◽  
pp. 04016036 ◽  
Author(s):  
Jianwen Xing ◽  
Baoguo Xiao ◽  
Ye Tian ◽  
Zhonghua Zheng
Keyword(s):  
Dual Mode ◽  
Scramjet Combustor ◽  
Constant Area ◽  
Area Section

Simple Identification of Electron Diffraction Ring Patterns

1969 ◽  
Vol 27 ◽  
pp. 160-161
Author(s):  
Carolyn Nohr ◽  
Ann Ayres
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Diffraction Ring ◽  
Image Position

Texts on electron diffraction recommend that the camera constant of the electron microscope be determine d by calibration with a standard crystalline specimen, using the equation

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