Wall pressure fluctuations in turbulent boundary layer flow over backward-facing step with and without entrainment were investigated. Digital array pressure sensors and multi-arrayed microphones were employed to acqui...Wall pressure fluctuations in turbulent boundary layer flow over backward-facing step with and without entrainment were investigated. Digital array pressure sensors and multi-arrayed microphones were employed to acquire the time-averaged static pressure and fluctuating pressure, respectively. The differences of two flows were scrutinized in terms of static pressure characteristics, pressure fluctuations, cross-correlation and coherence of wall pressure. Introduction of the entrainment increased scale of large-scale vortical structure and reduced its convection velocity. However, shedding frequency of large-scale vortical structures was found to be the same for both flows.展开更多
Based on the measured results that wall pressure fluctuations are mainly de- cided by coherent structures of turbulence, the relationship between root-mean- square wall pressure and wall shear stress in turbulent shea...Based on the measured results that wall pressure fluctuations are mainly de- cided by coherent structures of turbulence, the relationship between root-mean- square wall pressure and wall shear stress in turbulent shear flow and that between the intensities of pressure and fluctuating velocity in homogeneous and isotropic turbulence are established in this paper. These relationships are consistent with former works, and have good agreement with experimental data. The paper also dis- cusses the concept of 'apparent pressure' on the wall in mean flow.展开更多
Wall pressure fluctuation is one of the source terms which result in thevibration of hydraulic structures. To consider both the space and time correlation of the pressurefield. the method of proper orthogonal decompos...Wall pressure fluctuation is one of the source terms which result in thevibration of hydraulic structures. To consider both the space and time correlation of the pressurefield. the method of proper orthogonal decomposition and low-dimensional approximation were usedhere to describe the pressure signals of the turbulent boundary layer, the apron of the stillingpond and the vertically impinging jet.展开更多
In this paper theoretical wall pressure fluctuation spectrum calculated by Rapid Distortion Theory was used to predict the effect of circular transducer size on the measured statistical properties of wall pressure flu...In this paper theoretical wall pressure fluctuation spectrum calculated by Rapid Distortion Theory was used to predict the effect of circular transducer size on the measured statistical properties of wall pressure fluctuation signals. It was found that the measured onedimensional spectrum has a significant decreaSe at hish wave numbers due to attenuation by the finite size of the transducer, and wall pressure fluctuahon intensity decreases with the increase of the transducer size.展开更多
A new view of the spatial relation between fluctuating wall pressure and near-wall streamwise vortices （NWSV） is proposed for wall bounded turbulent flow by use of the direct numerical simulation （DNS） database. T...A new view of the spatial relation between fluctuating wall pressure and near-wall streamwise vortices （NWSV） is proposed for wall bounded turbulent flow by use of the direct numerical simulation （DNS） database. The results show that the wall region with low pressure forms just below the strong NWSV, which is mostly associated with the overhead NWSV. The wall region with high pressure forms downstream of the NWSV, which has a good correspondence with the downwash of the fluids induced by the upstream NWSV. The results provide a significant basis for the detection of NWSV.展开更多
Unsteady behaviors of the large-scale vortical structure superimposed in the turbulent separated and reattaching flow over a backward-facing step were convincingly delineated by performing simultaneous measurements of...Unsteady behaviors of the large-scale vortical structure superimposed in the turbulent separated and reattaching flow over a backward-facing step were convincingly delineated by performing simultaneous measurements of the wall pressure fluctuations and visualizations of the flow. Toward this end, a synchronized instrumentation system integrated with the microphone array and the high-speed camera was established. The smoke-wire technique was employed to visualize the unsteady events. A thorough analysis based on the wall pressure fluctuations disclosed that the large-scale vortical structure shedding at the frequency of fH/Uo = 0.064 gave a primary contribution to the wall pressure fluctuations, and consequently dominated unsteady behaviors of the turbulent shear layer. The convection velocity of the large-scale vortical structure was determined as Uc =0.55 U0. The instantaneous flow visualizations and wall pressure were compared in a straightforward manner. Below the separation bubble and the reattachment zone, the negative peak of the time-varying wall pressure was in phase with passage of the local large-scale vortical structure. In the redeveloping turbulent boundary layer, the decaying large-scale vortical structure was clearly revealed.展开更多
The unsteady behavior of the large-scale vortical structures buried in a wall-bounded turbulent shear layer flow was extensively investigated using pressure-velocity joint measurements. The wall pressure fluctuations ...The unsteady behavior of the large-scale vortical structures buried in a wall-bounded turbulent shear layer flow was extensively investigated using pressure-velocity joint measurements. The wall pressure fluctuations and flow field velocity fluctuations were measured simultaneously by using a microphone and an X-type hotwire, respectively. The spatially and temporally strong coupling between the convecting flow structures and the wall pressure fluctuations were meticulously investigated in terms of the continuous wavelet transform, cross-correlation and coherence of the wall pressure and flow field. The characteristics of the large-scale vortical structures, e.g., the shedding frequency, averaged convection velocity, convective motion, and structure pattern were revealed.展开更多
Spatio-temporal characteristics of the wall-bounded turbulent mixing layer flow over an open step and a square-edged rib were extensively studied in a low-speed wind tunnel. Simultaneous measurements of wall-pressure ...Spatio-temporal characteristics of the wall-bounded turbulent mixing layer flow over an open step and a square-edged rib were extensively studied in a low-speed wind tunnel. Simultaneous measurements of wall-pressure fluctuations and velocity measurements were performed by using microphone array and X-wire/split fim, respectively.展开更多
文摘Wall pressure fluctuations in turbulent boundary layer flow over backward-facing step with and without entrainment were investigated. Digital array pressure sensors and multi-arrayed microphones were employed to acquire the time-averaged static pressure and fluctuating pressure, respectively. The differences of two flows were scrutinized in terms of static pressure characteristics, pressure fluctuations, cross-correlation and coherence of wall pressure. Introduction of the entrainment increased scale of large-scale vortical structure and reduced its convection velocity. However, shedding frequency of large-scale vortical structures was found to be the same for both flows.
文摘Based on the measured results that wall pressure fluctuations are mainly de- cided by coherent structures of turbulence, the relationship between root-mean- square wall pressure and wall shear stress in turbulent shear flow and that between the intensities of pressure and fluctuating velocity in homogeneous and isotropic turbulence are established in this paper. These relationships are consistent with former works, and have good agreement with experimental data. The paper also dis- cusses the concept of 'apparent pressure' on the wall in mean flow.
文摘Wall pressure fluctuation is one of the source terms which result in thevibration of hydraulic structures. To consider both the space and time correlation of the pressurefield. the method of proper orthogonal decomposition and low-dimensional approximation were usedhere to describe the pressure signals of the turbulent boundary layer, the apron of the stillingpond and the vertically impinging jet.
文摘In this paper theoretical wall pressure fluctuation spectrum calculated by Rapid Distortion Theory was used to predict the effect of circular transducer size on the measured statistical properties of wall pressure fluctuation signals. It was found that the measured onedimensional spectrum has a significant decreaSe at hish wave numbers due to attenuation by the finite size of the transducer, and wall pressure fluctuahon intensity decreases with the increase of the transducer size.
基金Project supported by the National Natural Science Foundation of China(No.11402088)the Fundamental Research Funds for the Central Universities(No.2014MS33)the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(No.LAPS15005)
文摘A new view of the spatial relation between fluctuating wall pressure and near-wall streamwise vortices （NWSV） is proposed for wall bounded turbulent flow by use of the direct numerical simulation （DNS） database. The results show that the wall region with low pressure forms just below the strong NWSV, which is mostly associated with the overhead NWSV. The wall region with high pressure forms downstream of the NWSV, which has a good correspondence with the downwash of the fluids induced by the upstream NWSV. The results provide a significant basis for the detection of NWSV.
文摘Unsteady behaviors of the large-scale vortical structure superimposed in the turbulent separated and reattaching flow over a backward-facing step were convincingly delineated by performing simultaneous measurements of the wall pressure fluctuations and visualizations of the flow. Toward this end, a synchronized instrumentation system integrated with the microphone array and the high-speed camera was established. The smoke-wire technique was employed to visualize the unsteady events. A thorough analysis based on the wall pressure fluctuations disclosed that the large-scale vortical structure shedding at the frequency of fH/Uo = 0.064 gave a primary contribution to the wall pressure fluctuations, and consequently dominated unsteady behaviors of the turbulent shear layer. The convection velocity of the large-scale vortical structure was determined as Uc =0.55 U0. The instantaneous flow visualizations and wall pressure were compared in a straightforward manner. Below the separation bubble and the reattachment zone, the negative peak of the time-varying wall pressure was in phase with passage of the local large-scale vortical structure. In the redeveloping turbulent boundary layer, the decaying large-scale vortical structure was clearly revealed.
文摘The unsteady behavior of the large-scale vortical structures buried in a wall-bounded turbulent shear layer flow was extensively investigated using pressure-velocity joint measurements. The wall pressure fluctuations and flow field velocity fluctuations were measured simultaneously by using a microphone and an X-type hotwire, respectively. The spatially and temporally strong coupling between the convecting flow structures and the wall pressure fluctuations were meticulously investigated in terms of the continuous wavelet transform, cross-correlation and coherence of the wall pressure and flow field. The characteristics of the large-scale vortical structures, e.g., the shedding frequency, averaged convection velocity, convective motion, and structure pattern were revealed.
文摘Spatio-temporal characteristics of the wall-bounded turbulent mixing layer flow over an open step and a square-edged rib were extensively studied in a low-speed wind tunnel. Simultaneous measurements of wall-pressure fluctuations and velocity measurements were performed by using microphone array and X-wire/split fim, respectively.
