Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, ...Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, base drag reduction on the riblet surface, and flow control behaviors of riblet surface near the wall. The simulation results show that the riblet surface arranged on the rearward of the revolution body can reduce the skin friction drag by 8.27%, the base drag by 9.91% and the total drag by 8.59% at Ma number 0.8. The riblet surface reduces the skin friction drag by reducing the velocity gradient and turbulent intensity, and reduces the base drag by weakening the pumping action on the dead water region which behind the body of revolution caused by the external flow. The flow control behavior on boundary layer shows that the riblet surface can cut the low-speed flow near the wall effectively, and restrain the low-speed flow concentrating in span direction, thus weaken the instability of the low speed steaks produced by turbulent flow bursting.展开更多
Many factors such as outer diameter, hub ratio, blade numbers, shape and stagger angle affect the performance of small cooling fans. A small cooling fan was simulated using CFD software for three blade stagger angles ...Many factors such as outer diameter, hub ratio, blade numbers, shape and stagger angle affect the performance of small cooling fans. A small cooling fan was simulated using CFD software for three blade stagger angles （30.5°, 37.5°, 44.5°）and obtained the internal flow field and the static characteristics. Research indicated that the stagger angle has an obvious effect on the static characteristics of a fan. For flow rates below 0.0104 mVs, total pressure is the greatest when the stagger angle is 37.5°; flow rates higher than 0.0104 m^3/s, the total pressure is greatest when the stagger angle is 44.5° For the same flow rates, the velocity at inlet of pressure surface increases with in- creasing stagger angle, but the change of velocity on the suction surface is very small. For one model, vortices and the speed of revolution surfaces decrease with tip clearance increasing. But for other three models, increasing the stagger angle, the vortex intensity and speed of revolution surfaces at same height tip clearance increases, simultaneously, the position of vortex offset from the top of the rotor blade to the suction surface.展开更多
Numerical simulation on the flow fields near the dimpled and the smooth revolution bodies are performed and compared by using SST k-ω turbulence model, to explain the reasons of friction and base drag reductions on t...Numerical simulation on the flow fields near the dimpled and the smooth revolution bodies are performed and compared by using SST k-ω turbulence model, to explain the reasons of friction and base drag reductions on the bionic dimpled surface and the control behaviors of dimpled surface to boundary layer near wall of the revolution body. The simulation results show that the dimpled surface reduces the skin friction drag through reducing the velocity gradient and turbulent intensity, and reduces the base drag through weakening the pumping action on the flow behind the revolution body caused by the external flow; the low speed rotating vortexes in the dimples segregate the external flow and the revolution body; and the low speed rotating vortexes forming in the bottom of dimples can produce negative skin friction.展开更多
Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique oppor- tunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous m...Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique oppor- tunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous major global geological events.The basin had undergone three stages of tectonic evolution during the Late Jurassic and Cretaceous:syn-rifting phase,post-rifting thermal subsidence phase and basin inversion phase.The shallow strata of Yaojia Formation contain excellent Putaohua and Sartu reservoir rocks,which contribute great to the giant展开更多
In this paper, we establish the L^p （R-n＋1） boundedness for the commutators of singular integrals associated to surfaces of revolution, { （t,Ф （ ｜ t｜ ） ）： t ∈R^n }, with rough kernels Ω∈ L（IogL）^2（sn...In this paper, we establish the L^p （R-n＋1） boundedness for the commutators of singular integrals associated to surfaces of revolution, { （t,Ф （ ｜ t｜ ） ）： t ∈R^n }, with rough kernels Ω∈ L（IogL）^2（sn^-1）, if Ф（｜t｜） = ｜t｜.展开更多
Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique opportunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous maj...Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique opportunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous major global geological events.The basin had been undergone three stages of tectonic evolution during展开更多
In this paper, the authors establish the Lp-mapping properties of a class of singular integral operators along surfaces of revolution with rough kernels. The size condition on the kernels is optimal and much weaker th...In this paper, the authors establish the Lp-mapping properties of a class of singular integral operators along surfaces of revolution with rough kernels. The size condition on the kernels is optimal and much weaker than that for the classical Calderon-Zygmund singular integral operators.展开更多
基金supported by the Base Platform Construction Project of Jilin University Basic Scientific Research (Grant No 421060202466)the Technology Development Plan Project of Jilin Province (Grant No 20096032)+2 种基金the Youth Research Foundation of the Jilin University Agron-omy Faculty (Grant No 4305050102k7)the Key Program of National Natural Science Foundation of China (Grant No 50635030)the Ma-jor Program of the Science and Technology Development of Jilin Province (Grant No 09ZDGG001)
文摘Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, base drag reduction on the riblet surface, and flow control behaviors of riblet surface near the wall. The simulation results show that the riblet surface arranged on the rearward of the revolution body can reduce the skin friction drag by 8.27%, the base drag by 9.91% and the total drag by 8.59% at Ma number 0.8. The riblet surface reduces the skin friction drag by reducing the velocity gradient and turbulent intensity, and reduces the base drag by weakening the pumping action on the dead water region which behind the body of revolution caused by the external flow. The flow control behavior on boundary layer shows that the riblet surface can cut the low-speed flow near the wall effectively, and restrain the low-speed flow concentrating in span direction, thus weaken the instability of the low speed steaks produced by turbulent flow bursting.
基金support of Zhejiang Provincial Natural Science Foundation (No.R107635)Zhejiang Provincial Key Science Foundation (2008 C11027)National Natural Science Foundation of China (No.50735004)
文摘Many factors such as outer diameter, hub ratio, blade numbers, shape and stagger angle affect the performance of small cooling fans. A small cooling fan was simulated using CFD software for three blade stagger angles （30.5°, 37.5°, 44.5°）and obtained the internal flow field and the static characteristics. Research indicated that the stagger angle has an obvious effect on the static characteristics of a fan. For flow rates below 0.0104 mVs, total pressure is the greatest when the stagger angle is 37.5°; flow rates higher than 0.0104 m^3/s, the total pressure is greatest when the stagger angle is 44.5° For the same flow rates, the velocity at inlet of pressure surface increases with in- creasing stagger angle, but the change of velocity on the suction surface is very small. For one model, vortices and the speed of revolution surfaces decrease with tip clearance increasing. But for other three models, increasing the stagger angle, the vortex intensity and speed of revolution surfaces at same height tip clearance increases, simultaneously, the position of vortex offset from the top of the rotor blade to the suction surface.
基金Sponsored by the National Natural Science Foundation of China (50635030)the Technology Development Plan of Jilin Province ( 20096032)+1 种基金the Major Program of Science and Technology Development of Jilin Province (09ZDGG001)the Youth Research Start-up Fund of Agriculture Department of Jilin University ( 4305050102K7)
文摘Numerical simulation on the flow fields near the dimpled and the smooth revolution bodies are performed and compared by using SST k-ω turbulence model, to explain the reasons of friction and base drag reductions on the bionic dimpled surface and the control behaviors of dimpled surface to boundary layer near wall of the revolution body. The simulation results show that the dimpled surface reduces the skin friction drag through reducing the velocity gradient and turbulent intensity, and reduces the base drag through weakening the pumping action on the flow behind the revolution body caused by the external flow; the low speed rotating vortexes in the dimples segregate the external flow and the revolution body; and the low speed rotating vortexes forming in the bottom of dimples can produce negative skin friction.
文摘Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique oppor- tunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous major global geological events.The basin had undergone three stages of tectonic evolution during the Late Jurassic and Cretaceous:syn-rifting phase,post-rifting thermal subsidence phase and basin inversion phase.The shallow strata of Yaojia Formation contain excellent Putaohua and Sartu reservoir rocks,which contribute great to the giant
基金supported by NSF of China(Grant No.11471033)NCET of China(Grant No.NCET-11-0574)the Fundamental Research Funds for the Central Universities(FRF-TP-12-006B)
文摘In this paper, we establish the L^p （R-n＋1） boundedness for the commutators of singular integrals associated to surfaces of revolution, { （t,Ф （ ｜ t｜ ） ）： t ∈R^n }, with rough kernels Ω∈ L（IogL）^2（sn^-1）, if Ф（｜t｜） = ｜t｜.
文摘Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique opportunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous major global geological events.The basin had been undergone three stages of tectonic evolution during
文摘In this paper, the authors establish the Lp-mapping properties of a class of singular integral operators along surfaces of revolution with rough kernels. The size condition on the kernels is optimal and much weaker than that for the classical Calderon-Zygmund singular integral operators.
