scholarly journals A numerical investigation on the vortex formation and flow separation of the oscillatory flow in jet pumps

2015 ◽  
Vol 137 (4) ◽  
pp. 1722-1731 ◽  
Author(s):  
Joris P. Oosterhuis ◽  
Simon Bühler ◽  
Theo H. van der Meer ◽  
Douglas Wilcox
Keyword(s):  
Numerical Investigation ◽  
Flow Separation ◽  
Oscillatory Flow ◽  
Vortex Formation ◽  
Jet Pumps

Numerical Investigation of Cowl Lip Adjustments for a Rocket-Based Combined-Cycle Inlet in Takeoff Regime

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Lei Shi ◽  
Xiaowei Liu ◽  
Guoqiang He ◽  
Fei Qin ◽  
Xianggeng Wei ◽  
...  
Keyword(s):  
Numerical Integration ◽  
Numerical Investigation ◽  
Flow Separation ◽  
Static Condition ◽  
Combined Cycle ◽  
Variable Geometry ◽  
Overall Performance ◽  
Negative Impacts

AbstractNumerical integration simulations were performed on a ready-made central strut-based rocket-based combined-cycle (RBCC) engine operating in the ejector mode during the takeoff regime. The effective principles of various cowl lip positions and shapes on the inlet operation and the overall performance of the entire engine were investigated in detail. Under the static condition, reverse cowl lip rotation in a certain range was found to contribute comprehensive improvement to the RBCC inlet and the entire engine. However, the reverse rotation of the cowl lip contributed very little enhancement of the RBCC inlet under the low subsonic flight regime and induced extremely negative impacts in the high subsonic flight regime, especially in terms of a significant increase in the drag of the inlet. Changes to the cowl lip shape provided little improvement to the overall performance of the RBCC engine, merely shifting the location of the leeward area inside the RBCC inlet, as well as the flow separation and eddy, but not relieving or eliminating those phenomena. The results of this study indicate that proper cowl lip rotation offers an efficient variable geometry scheme for a RBCC inlet in the takeoff regime.

Performance comparison of jet pumps with round and sharp edge of small opening in oscillatory flow

2018 ◽  
Vol 139 ◽  
pp. 562-568 ◽  
Author(s):  
Ye Feng ◽  
Ke Tang ◽  
Tao Jin ◽  
Kaihao Zhang ◽  
Rui Yang
Keyword(s):  
Oscillatory Flow ◽  
Performance Comparison ◽  
Sharp Edge ◽  
Small Opening ◽  
Jet Pumps

scholarly journals Experimental and numerical investigation of the vortex formation process behind a heated cylinder

2004 ◽  
Vol 16 (8) ◽  
pp. 3103-3114 ◽  
Author(s):  
Maosheng Ren ◽  
Camilo C. M. Rindt ◽  
Anton A. van Steenhoven
Keyword(s):  
Numerical Investigation ◽  
Formation Process ◽  
Vortex Formation ◽  
Heated Cylinder

Turbulent wake of an inclined cylinder with water running

2007 ◽  
Vol 589 ◽  
pp. 261-303 ◽  
Author(s):  
MD. MAHBUB ALAM ◽  
Y. ZHOU
Keyword(s):  
Fluid Dynamics ◽  
Stagnation Point ◽  
Vortex Shedding ◽  
Flow Separation ◽  
Vortex Formation ◽  
Cylinder Surface ◽  
Stagnation Line ◽  
Separation Line ◽  
Fluid Forces ◽  
Aerodynamic Pressure

This paper presents the results of an experimental study of fluid dynamics around an inclined circular cylinder with and without water running over its surface, covering water rivulet formation, fluid forces on the cylinder, near wake and their interrelationships. The cylinder inclination angle (α) with respect to incident flow was between 55° and 80°. It has been found that water running over the cylinder surface may behave quite differently, depending on the Reynolds number (Re), and subsequently impact greatly upon the fluid dynamics around the cylinder. As such, five flow categories are classified. Category A: one water rivulet was observed, irrespective of α, at the leading stagnation point at a small Re. Category B: the rivulet splits into two, symmetrically arranged about the leading stagnation line, once Re exceeds a critical value that depends on α. The two rivulets may further switch back to one, and vice versa. Category C: two symmetrical straight rivulets occur. Category D: the two rivulets shift towards the flow separation line with increasing Re and oscillate circumferentially. The oscillation reaches significant amplitude when the rivulets occur at about 70° from the leading stagnation point. This increased amplitude is coupled with a rapid climb in the mean and fluctuating drag and lift, by a factor of near 5 for the fluctuating lift at α = 80°. Meanwhile, the flow structure exhibits a marked variation. For example, Strouhal number and vortex formation length decrease, along with an increase in spanwise vorticity concentration, velocity deficit, and coherence between vortex shedding and fluctuating lift. All these observations point to the occurrence of a ‘lock-in’ phenomenon, i.e. the rivulet oscillation synchronizing with flow separation. A rivulet–vortex-induced instability is proposed to be responsible for the well reported rain–wind-induced vibration associated with the stay cables of cable-stayed bridges. Category E: the two rivulets shift further downstream just beyond the separation line; the shear layers behind the rivulets become highly turbulent, resulting in weakened vortex shedding, flow fluctuating velocities and fluctuating fluid forces. Based on the equilibrium of water rivulet weight, aerodynamic pressure and friction force between fluid and surface, an analysis is developed to predict the rivulet position on the cylinder, which agrees well with measurements.

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