Blasius–Rayleigh–Stokes flow of nanofluid past an isothermal magnetized surface

The present article investigated the unsteady flow of a nanofluid past an isothermal magnetized plate emanating from a moving slot. This unique form of unsteady boundary layer flow is analogous to stretching/shrinking sheet problems subject to the direction of motion of the slot. Governing partial differential equation can be reduced into a similar form using the Blasius–Rayleigh–Stokes variable. The consequences of the movable slot and magnetic field on flow and heat transfer of nanofluid are examined by solving the problem numerically. The behavior of the magnetic field in the presence of nanoparticles is also examined. Effects of the magnetic field upon the existence of dual solutions for the specific range of moving slot parameter are also studied in detail.

Unsteady Boundary Layer Flow Over a Permeable Stretching/Shrinking Cylinder Immersed in Nanofluid

In this study, the unsteady boundary layer flow over a stretching/shrinking cylinder immersed in nanofluid with the presence of suction effect is analyzed. The governing partial differential equations are converted to ordinary differential equations by introducing similarity transformation variables. The shooting method is applied to solve the system where the numerical solutions are obtained and presented graphically. The study's objective is to investigate the effect of nanoparticle volume fraction, the unsteadiness parameter, the stretching/shrinking parameter on the velocity and temperature gradients. It is found that the dual solutions are obtained in a specific range of these parameters for both stretching and shrinking cylinders. Besides, a high volume of the nanoparticle in the base fluid increases the velocity gradient and decreases the temperature gradient at the surface. Also, increasing nanoparticle volume fraction in the base fluid expands the solution's range, which denotes the boundary layer separation from the surface has been delayed. The existence of dual solutions allows stability analysis performance by introducing a new dimensionless variable and is solved using bvp4c function in Matlab software. This phase obtains the smallest eigenvalue, showing that the first solution is stable and physically realizable while the second solution is not stable.

Numerical Investigation of Unsteady Boundary Layer Transition on a Dynamically Pitching Rotor

Predictions of unsteady boundary layer transition are performed on a four-bladed rotor in axial inflow using a computational fluid dynamics approach. The configuration is based on experiments performed at the German Aerospace Center (DLR) in the 1.6-m × 3.4-m wind tunnel in the rotor test facility (RTG). Simulations are performed using the NASA OVERFLOW 2.3 solver with hybrid RANS/LES and laminar turbulent transition modeling. Solutions are based on a hover tip Mach number of 0.143 with prescribed cyclic pitching conditions. Computational methods and grid generation are described. The rotor flow field is analyzed, and the effect of transition modeling on unsteady boundary layer transition prediction is assessed. Laminar-turbulent transition predictions and rotor performance are compared to experimental measurements obtained at the DLR RTG. A study of sensitivity was performed on freestream turbulence intensity to investigate its effect on predicted rotor transition.

Unsteady Boundary Layer Flow of a Micropolar Fluid at a Two-Dimensional Stagnation Point on a Moving Wall

The problem of unsteady boundary layer flow of a micropolar fluid at a two-dimensional stagnation point on a moving wall when the free stream velocity and wall temperature vary arbitrarily with time has been studied. The governing partial differential equations were solved numerically by the Keller box method. The micropolar fluid flow model on a moving wall is capable of predicting the results which exhibit turbulent flow characteristics. Numerical results obtained for velocity, micro rotations and temperature distributions are shown graphically. The velocity distribution has been illustrated for several positive and negative values of the wall velocity. The skin friction, couple stress and transfer rate are found to be strongly dependent on the coupling parameter and time, however the effect of variation in the micro rotation parameter is visible appreciably in case of couple stress only.

Unsteady Boundary Layer Stagnation Point Flow and Heat Transfer over a Stretching Sheet in a Porous Medium with Slip Effects

Boundary layer flow and heat transfer over a stretching sheet in a porous medium has many applications in industrial processes. The effect of porosity plays a significant role in determining the behaviour of the fluid flow. Based on that, we analyzed the unsteady boundary layer stagnation point flow and heat transfer towards a stretching sheet by considering the porosity. The velocity and thermal slip effects are taken into consideration in the present analysis. The governing non-linear partial differential equations were transformed into a system of nonlinear ordinary differential equations using similarity transformation. The resulting ordinary differential equations were solved numerically using the shooting method in Maple software. Numerical results for the dimensionless velocity profile, temperature profile, skin friction coefficients and the local Nusselt number are presented for various parameters. The effect of dimensionless material parameter, thermal slip effect and velocity slip effect on the flow field is also discussed. It is found that the skin friction coefficients decrease whereas the local Nusselt number increases with the increase in permeability parameter.