Experimental investigations of spatial structure of turbulent pressure fluctuations in a wall-bounded turbulent flow

2008 ◽  
Author(s):  
Efim Kudashev ◽  
Bengt Enflo ◽  
Claes M. Hedberg ◽  
Leif Kari
Keyword(s):  
Spatial Structure ◽  
Turbulent Flow ◽  
Pressure Fluctuations ◽  
Experimental Investigations ◽  
Turbulent Pressure

Numerical Simulation of Turbulent Flow Past a Serrated Airfoil

2011 ◽  
Author(s):  
Changhwa Han ◽  
Takeshi Omori ◽  
Takeo Kajishima
Keyword(s):  
Turbulent Flow ◽  
Pressure Fluctuations ◽  
Density Variation ◽  
Aerodynamic Noise ◽  
Experimental Investigations ◽  
Frequency Noise ◽  
Trailing Edge ◽  
Eddy Simulation ◽  
Naca0012 Airfoil ◽  
Edge Side

Despite a lot of experimental investigations, the effect of airfoil serrations on the reduction of discrete frequency noise (DFN) is not fully understood. We apply the large-eddy simulation (LES) to the turbulent flow around the NACA0012 airfoil without angle of attack in a uniform stream. In this case, a major source of aerodynamic noise is quasi two-dimensional spanwise vortices, which take place near the trailing edge. We therefore investigate the effect of serration in the trailing edge side. The depth of the serration is 10% of chord length. To take into account the weak compressibility at low Mach number, we made a particular modification to the pressure equation. One equation dynamic model for the subgrid scale stress is used for LES. These techniques have originally been developed in our research group. The serration successfully reduced the pressure fluctuations on the surface of the airfoil near the trailing edge. The observed structure of the density variation suggests that this modification contributes to the reduction of sound source.

Effects of inlet radial distortion on the type of stall precursor in low-speed axial compressor

2016 ◽  
Vol 232 (1) ◽  
pp. 55-67 ◽  
Author(s):  
Ali Arshad ◽  
Qiushi Li ◽  
Simin Li ◽  
Tianyu Pan
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Experimental Investigations ◽  
Inlet Flow ◽  
Blade Loading ◽  
Stall Inception ◽  
Low Speed ◽  
Modal Type ◽  
Stall Precursor

Experimental investigations of the effect of inlet blade loading on the rotating stall inception process are carried out on a single-stage low-speed axial compressor. Temporal pressure signals from the six high response pressure transducers are used for the analysis. Pressure variations at the hub are especially recorded during the stall inception process. Inlet blade loading is altered by installing metallic meshed distortion screens at the rotor upstream. Three sets of experiments are performed for the comparison of results, i.e. uniform inlet flow, tip, and hub distortions, respectively. Regardless of the type of distortion introduced to the inflow, the compressor undergoes a performance drop, which is more severe in the hub distortion case. Under the uniform inlet flow condition, stall inception is caused by the modal type disturbance while the stall precursor switched to spike type due to the highly loaded blade tip. In the presence of high blade loading at the hub, spike disappeared and the compressor once again witnessed a modal type disturbance. Hub pressure fluctuations are observed throughout the process when the stall is caused by a modal wave while no disturbance is noticed at the hub in spike type stall inception. It is believed that the hub flow separation contributes to the modal type of stall inception phenomenon. Results are also supported by the recently developed signal processing techniques for the stall inception study.

Computerized Model of Transition in Circular Pipe Flows: Part 1 — Experimental Definition of the Problem

1999 ◽  
Author(s):  
Hidesada Kanda
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Critical Reynolds Number ◽  
Natural Disturbance ◽  
Reynolds Numbers ◽  
Entrance Region ◽  
Circular Pipe ◽  
Experimental Investigations ◽  
Circular Pipes ◽  
Definition Of

Abstract A conceptual model was constructed for the problem of determining in circular pipes the conditions under which the transition from laminar to turbulent flow occurs, so that it becomes possible to calculate the minimum critical Reynolds number. Up until now this problem has been investigated by stability theory with disturbances at the pipe inlet. However, the minimum critical Reynolds number has not yet been obtained theoretically. Hence, the author took up the problem directly from many previous experimental investigations and found that (i) plots of the transition length versus the Reynolds number show that the transition occurs in the entrance region under the condition of a natural disturbance, and (ii) plots of the critical Reynolds number versus the ratio of bellmouth diameter to the pipe diamter show that with larger shapes of bellmouths, laminar flow will persist to higher Reynolds numbers. The problem is thus defined clearly as: Under the condition of an ordinary disturbance, the transition from laminar to turbulent flow occurs in the entrance region of a straight circular pipe, then the Reynolds number takes a minimum value of about 2000.

Influence of wall roughness on the static performance and pressure fluctuation characteristics of a double-suction centrifugal pump

2018 ◽  
Vol 232 (7) ◽  
pp. 826-840 ◽  
Author(s):  
Zhifeng Yao ◽  
Min Yang ◽  
Ruofu Xiao ◽  
Fujun Wang
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Design Flow ◽  
Experimental Investigations ◽  
Wall Roughness ◽  
Detached Eddy Simulation ◽  
Centrifugal Pumps ◽  
Eddy Simulation ◽  
Static Performance

The unsteady flow field and pressure fluctuations in double-suction centrifugal pumps are greatly affected by the wall roughness of internal surfaces. To determine the wall roughness effect, numerical and experimental investigations were carried out. Three impeller schemes for different wall roughness were solved using detached eddy simulation, and the performance and pressure fluctuations resolved by detached eddy simulation were compared with the experimental data. The results show that the effects of wall roughness on the static performance of a pump are remarkable. The head and efficiency of the tested double-suction centrifugal pump are raised by 2.53% and 6.60% respectively as the wall roughness is reduced by means of sand blasting and coating treatments. The detached eddy simulation method has been proven to be accurate for the prediction of the head and efficiency of the double-suction centrifugal pump with roughness effects. The influence of the roughness on pressure fluctuation is greatly dependent on the location relative to the volute tongue region. For locations close to the volute tongue, the peak-to-peak value of the pressure fluctuations of a wall roughness of Ra = 0.10 mm may be 23.27% larger than the case where Ra = 0.02 mm at design flow rate.

Density and Pressure Fluctuations in a Turbulent Flow of Air and Argon and Their Interaction with a Shock Wave

2019 ◽  
Vol 74 (3) ◽  
pp. 256-261
Author(s):  
O. I. Dokukina ◽  
E. N. Terentiev ◽  
L. S. Shtemenko ◽  
F. V. Shugaev
Keyword(s):  
Shock Wave ◽  
Turbulent Flow ◽  
Pressure Fluctuations
Sign in / Sign up

Export Citation Format

Share Document