A numerical analysis of the log-law behavior for the turbulent boundary layer of a wall-bounded flow is performed over a flat plate immersed in three nanofluids(Zn O-water,SiO_(2)-water,TiO_(2)-water).Numerical simula...A numerical analysis of the log-law behavior for the turbulent boundary layer of a wall-bounded flow is performed over a flat plate immersed in three nanofluids(Zn O-water,SiO_(2)-water,TiO_(2)-water).Numerical simulations using CFD code are employed to investigate the boundary layer and the hydrodynamic flow.To validate the current numerical model,measurement points from published works were used,and the compared results were in good compliance.Simulations were carried out for the velocity series of 0.04,0.4 and 4 m/s and nanoparticle concentrations0.1% and 5%.The influence of nanoparticles’ concentration on velocity,temperature profiles,wall shear stress,and turbulent intensity was investigated.The obtained results showed that the viscous sub-layer,the buffer layer,and the loglaw layer along the potential-flow layer could be analyzed based on their curving quality in the regions which have just a single wall distance.It was seen that the viscous sub-layer is the biggest area in comparison with other areas.Alternatively,the section where the temperature changes considerably correspond to the thermal boundary layer’s thickness goes a downward trend when the velocity decreases.The thermal boundary layer gets deep away from the leading edge.However,a rise in the volume fraction of nanoparticles indicated a minor impact on the shear stress developed in the wall.In all cases,the thickness of the boundary layer undergoes a downward trend as the velocity increases,whereas increasing the nanoparticle concentrations would enhance the thickness.More precisely,the log layer is closed with log law,and it is minimal between Y^(+)=50 and Y^(+)=95.The temperature for nanoparticle concentration φ=5%is higher than that for φ=0.1%,in boundary layers,for all studied nanofluids.However,it is established that the behavior is inverted from the value of Y^(+)=1 and the temperature for φ =0.1% is more important than the case of φ =5%.For turbulence intensity peak,this peak exists at Y^(+)=100 for v=4 m/s,Y^(+)=10 for v=0.4 m/s and Y^(+)=8 for v=0.04 m/s.展开更多
饱和粉土在地震作用下会发生液化变形,从而导致建立在其上的建(构)筑物发生破坏。工程场地区域内粉土单元通常存在初始剪应力作用,为探究初始剪应力对饱和粉土液化特性的影响,将液化后粉土视为流体进行了一系列循环扭剪试验研究。试验...饱和粉土在地震作用下会发生液化变形,从而导致建立在其上的建(构)筑物发生破坏。工程场地区域内粉土单元通常存在初始剪应力作用,为探究初始剪应力对饱和粉土液化特性的影响,将液化后粉土视为流体进行了一系列循环扭剪试验研究。试验结果表明,初始剪应力对饱和粉土剪应力-剪应变率曲线影响显著,随着初始剪应力τ_(s)的增大,剪应力-剪应变率曲线由“椭圆形”向“哑铃形”过渡逐渐转变为由“镰刀形”向“椭圆形”至“锤形”过渡;表观黏度η与振次N的衰减曲线随着τ_(s)的增大先降低再抬升,平均流动系数κ与振次N的增长曲线发展速度随着τ_(s)的增大先加快后减慢,固液相变孔压比r_(uth)随着τ_(s)的增大先减小后增大,当τ_(s)=5 k Pa时饱和粉土的r_(uth)最小。展开更多
基金support he received through General Research Project under the grant number (R.G.P.2/138/42)。
文摘A numerical analysis of the log-law behavior for the turbulent boundary layer of a wall-bounded flow is performed over a flat plate immersed in three nanofluids(Zn O-water,SiO_(2)-water,TiO_(2)-water).Numerical simulations using CFD code are employed to investigate the boundary layer and the hydrodynamic flow.To validate the current numerical model,measurement points from published works were used,and the compared results were in good compliance.Simulations were carried out for the velocity series of 0.04,0.4 and 4 m/s and nanoparticle concentrations0.1% and 5%.The influence of nanoparticles’ concentration on velocity,temperature profiles,wall shear stress,and turbulent intensity was investigated.The obtained results showed that the viscous sub-layer,the buffer layer,and the loglaw layer along the potential-flow layer could be analyzed based on their curving quality in the regions which have just a single wall distance.It was seen that the viscous sub-layer is the biggest area in comparison with other areas.Alternatively,the section where the temperature changes considerably correspond to the thermal boundary layer’s thickness goes a downward trend when the velocity decreases.The thermal boundary layer gets deep away from the leading edge.However,a rise in the volume fraction of nanoparticles indicated a minor impact on the shear stress developed in the wall.In all cases,the thickness of the boundary layer undergoes a downward trend as the velocity increases,whereas increasing the nanoparticle concentrations would enhance the thickness.More precisely,the log layer is closed with log law,and it is minimal between Y^(+)=50 and Y^(+)=95.The temperature for nanoparticle concentration φ=5%is higher than that for φ=0.1%,in boundary layers,for all studied nanofluids.However,it is established that the behavior is inverted from the value of Y^(+)=1 and the temperature for φ =0.1% is more important than the case of φ =5%.For turbulence intensity peak,this peak exists at Y^(+)=100 for v=4 m/s,Y^(+)=10 for v=0.4 m/s and Y^(+)=8 for v=0.04 m/s.
文摘饱和粉土在地震作用下会发生液化变形,从而导致建立在其上的建(构)筑物发生破坏。工程场地区域内粉土单元通常存在初始剪应力作用,为探究初始剪应力对饱和粉土液化特性的影响,将液化后粉土视为流体进行了一系列循环扭剪试验研究。试验结果表明,初始剪应力对饱和粉土剪应力-剪应变率曲线影响显著,随着初始剪应力τ_(s)的增大,剪应力-剪应变率曲线由“椭圆形”向“哑铃形”过渡逐渐转变为由“镰刀形”向“椭圆形”至“锤形”过渡;表观黏度η与振次N的衰减曲线随着τ_(s)的增大先降低再抬升,平均流动系数κ与振次N的增长曲线发展速度随着τ_(s)的增大先加快后减慢,固液相变孔压比r_(uth)随着τ_(s)的增大先减小后增大,当τ_(s)=5 k Pa时饱和粉土的r_(uth)最小。
