A three-layer theoretical model is used to calculate the lee wave of a real example occurring over Blue Ridge in Pittsburgh, in which the maximum vertical velocity is 0.11 m s^-1. Based on this, the influence of chang...A three-layer theoretical model is used to calculate the lee wave of a real example occurring over Blue Ridge in Pittsburgh, in which the maximum vertical velocity is 0.11 m s^-1. Based on this, the influence of changes in the thickness and values of the Scorer parameter in each layer are analyzed. It is shown that the influence of each layer parameters on the lee-wave amplitude is different, and the amplitude is more sensitive to the changes in the lower layer. Since the environment changes can affect the Scorer parameter profile, the influence of the environment on the amplitude is studied. The results show that the amplitude will decrease in the daytime because of solar heating, and increase at night because of radiational cooling, according to observational data. The case is also simulated by the Advanced Regional Prediction System （ARPS） model. The simulated amplitude is 0.089 m s^-1, which is close to the calculated result. Numerical sensitivity experiments are performed to test the former calculated experiments. The simulated results are consistent with the analytically calculated results.展开更多
A three-layer theoretical model was established, in which the atmosphere is divided into three layers based on the Scorer parameter 12 , which is large in the middle layer and small in the other two layers. The wave n...A three-layer theoretical model was established, in which the atmosphere is divided into three layers based on the Scorer parameter 12 , which is large in the middle layer and small in the other two layers. The wave number formula of lee waves was deduced with this theoretical model, and a typical example for the lee wave was calculated. Thus, the influence of changes in the thickness of every layer and values of the Scorer parameter in every layer was examined. The results show that the wavelength decreases with an increase in the thickness of the lower and the middle layers and is more sensitive to the changes in the middle layer. Therefore, if the changes in these two layers are different, the changes in the middle layer will dominate the changes in the wavelength. The results also show that the wavelength decreases with the increase in the value of 12 in every layer, among which the sensitivity to the 12 in the upper layer is the most striking. The calculation results reasonably can explain the influence of diurnal changes on the wavelength. The example was simulated using Advanced Regional Prediction System model, and the sensitivity experiments were performed to confirm the effects of the Scorer parameter profiles on the wavelengths. The simulated results are consistent with the calculated results.展开更多
The cyclic behavior of lee wave systems, generated by stratified flow over mountains is investigated by the Advanced Regional Prediction System (ARPS) model. The results show that, surface friction has a direct impact...The cyclic behavior of lee wave systems, generated by stratified flow over mountains is investigated by the Advanced Regional Prediction System (ARPS) model. The results show that, surface friction has a direct impact upon the number and timing of mountain gravity waves cycle generation. Cyclic generation of mountain lee waves and down-slope winds was found to be extremely sensitive to the magnitude of the surface drag coefficient, where mountain waves amplitude and intensity varies with the magnitude of the drag coefficient, and the interaction of mountain waves and boundary layer process determinates the wave characteristics. For the typical drag Cd = 10–3, surface friction promotes the formation of the stationary mountain lee waves and hydraulic jump, especially, promotes boundary layer separation, the generation of low-level turbulent zones and rotor circulation or reversal flow within boundary layer. When drag coefficient becomes Cd = 10–4, lee waves remain steady states and the first evolution cycle maintains much longer than that of Cd = 10–3. In the case of the highest drag coefficient Cd = 10–2, surface friction suppresses wave breaking and the onset of hydraulic jump, and reduces greatly the amplitude and intensity of lee waves and down slope wind.展开更多
Supersonic wind tunnel experiment is one of the important measurements for developing advanced gas turbines,and supersonic multi-hole probes are sophisticated tools to measure pneumatic parameters in such experiments....Supersonic wind tunnel experiment is one of the important measurements for developing advanced gas turbines,and supersonic multi-hole probes are sophisticated tools to measure pneumatic parameters in such experiments.However,shock waves form around the probe head in supersonic flow,which affect the accuracy of results.In this study,a supersonic five-hole probe is selected as the research object.Firstly,a compound five-hole pressure-temperature probe was designed and produced with 3D-printing technology.Then,the shock wave spectrum was numerically calculated by three methods,which were the Mach number,density gradient,and shock function;in contrast to the other two methods,the shock function could accurately identify the types and ranges of shock and expansion waves.The results show that a strong shock wave is formed at the front section of the probe head,and the shock wave generated around the pressure measuring tube affects the total pressure and Mach number of the flow field,which causes the increase of entropy.The intensity of the shock wave at the head of the pressure measuring tube is the largest,causing a decrease in the total pressure around the flow field.Afterwards,to reduce the calculation errors caused by neglecting the compressibility of gases and the entropy increase,a gas compression factor δ_(s) was introduced.It is proved that the error of the calculated pneumatic parameters is less than 5% and 10% in subsonic and supersonic condition,respectively,with the gas compression factor considered.The research results of this paper provide theoretical reference for the design and use of pneumatic probes during subsonic to supersonic flow.展开更多
基金the National Natural Science Foundation of China （40705020）.
文摘A three-layer theoretical model is used to calculate the lee wave of a real example occurring over Blue Ridge in Pittsburgh, in which the maximum vertical velocity is 0.11 m s^-1. Based on this, the influence of changes in the thickness and values of the Scorer parameter in each layer are analyzed. It is shown that the influence of each layer parameters on the lee-wave amplitude is different, and the amplitude is more sensitive to the changes in the lower layer. Since the environment changes can affect the Scorer parameter profile, the influence of the environment on the amplitude is studied. The results show that the amplitude will decrease in the daytime because of solar heating, and increase at night because of radiational cooling, according to observational data. The case is also simulated by the Advanced Regional Prediction System （ARPS） model. The simulated amplitude is 0.089 m s^-1, which is close to the calculated result. Numerical sensitivity experiments are performed to test the former calculated experiments. The simulated results are consistent with the analytically calculated results.
基金Project supported by the Opening Foundation of LASGthe National Natural Science Foundation of China (Grant No. 40575023).
文摘A three-layer theoretical model was established, in which the atmosphere is divided into three layers based on the Scorer parameter 12 , which is large in the middle layer and small in the other two layers. The wave number formula of lee waves was deduced with this theoretical model, and a typical example for the lee wave was calculated. Thus, the influence of changes in the thickness of every layer and values of the Scorer parameter in every layer was examined. The results show that the wavelength decreases with an increase in the thickness of the lower and the middle layers and is more sensitive to the changes in the middle layer. Therefore, if the changes in these two layers are different, the changes in the middle layer will dominate the changes in the wavelength. The results also show that the wavelength decreases with the increase in the value of 12 in every layer, among which the sensitivity to the 12 in the upper layer is the most striking. The calculation results reasonably can explain the influence of diurnal changes on the wavelength. The example was simulated using Advanced Regional Prediction System model, and the sensitivity experiments were performed to confirm the effects of the Scorer parameter profiles on the wavelengths. The simulated results are consistent with the calculated results.
文摘The cyclic behavior of lee wave systems, generated by stratified flow over mountains is investigated by the Advanced Regional Prediction System (ARPS) model. The results show that, surface friction has a direct impact upon the number and timing of mountain gravity waves cycle generation. Cyclic generation of mountain lee waves and down-slope winds was found to be extremely sensitive to the magnitude of the surface drag coefficient, where mountain waves amplitude and intensity varies with the magnitude of the drag coefficient, and the interaction of mountain waves and boundary layer process determinates the wave characteristics. For the typical drag Cd = 10–3, surface friction promotes the formation of the stationary mountain lee waves and hydraulic jump, especially, promotes boundary layer separation, the generation of low-level turbulent zones and rotor circulation or reversal flow within boundary layer. When drag coefficient becomes Cd = 10–4, lee waves remain steady states and the first evolution cycle maintains much longer than that of Cd = 10–3. In the case of the highest drag coefficient Cd = 10–2, surface friction suppresses wave breaking and the onset of hydraulic jump, and reduces greatly the amplitude and intensity of lee waves and down slope wind.
基金co-supported by the National Natural Science Foundation of China(No.52236005)the Science Center for GasTurbineProject(No.P2022-B-II-007-001)the National Key Laboratory Funds(No.D5150230002).
文摘Supersonic wind tunnel experiment is one of the important measurements for developing advanced gas turbines,and supersonic multi-hole probes are sophisticated tools to measure pneumatic parameters in such experiments.However,shock waves form around the probe head in supersonic flow,which affect the accuracy of results.In this study,a supersonic five-hole probe is selected as the research object.Firstly,a compound five-hole pressure-temperature probe was designed and produced with 3D-printing technology.Then,the shock wave spectrum was numerically calculated by three methods,which were the Mach number,density gradient,and shock function;in contrast to the other two methods,the shock function could accurately identify the types and ranges of shock and expansion waves.The results show that a strong shock wave is formed at the front section of the probe head,and the shock wave generated around the pressure measuring tube affects the total pressure and Mach number of the flow field,which causes the increase of entropy.The intensity of the shock wave at the head of the pressure measuring tube is the largest,causing a decrease in the total pressure around the flow field.Afterwards,to reduce the calculation errors caused by neglecting the compressibility of gases and the entropy increase,a gas compression factor δ_(s) was introduced.It is proved that the error of the calculated pneumatic parameters is less than 5% and 10% in subsonic and supersonic condition,respectively,with the gas compression factor considered.The research results of this paper provide theoretical reference for the design and use of pneumatic probes during subsonic to supersonic flow.
