The ability of the interpolation supplemented lattice Boltzmann method (ISLBM) diminishes in simulation of fluid flow around complex geometries and it is nearly impossible to use this method in body-filled grid systems. In this paper, a developed version of the interpolation supplemented lattice Boltzmann method is proposed to remove the limitations of the original ISLBM. Combination of the ISLBM and the Joukowski transformation is the basis of the method. In fact, using the Joukowski transformation, the physical domain with a body-fitted grid system is mapped to the computational domain with a uniform Cartesian grid system such that the conventional ISLBM can be easily applied. The results are compared with those of a Navier-Stokes solver and there is good agreement between these two results.

Since the air density reduces as altitude increases, operation of small wind turbines (SWTs), which usually have no pitch adjustment, remains challenging at high altitudes due largely to the reduction of starting aerodynamic torque. By reducing the moment of inertia through the use of hollow blades, this study aims to speed up the starting while maintaining the structural integrity of the blades and high output power. A horizontal axis turbine with hollow blades was designed for two sites in Iran with altitude of 500 m and 3000 m. The design variables are the distributions of the chord, twist, and shell thickness and the improvement of output power and starting are the design goals. Blade-element momentum (BEM) theory was employed to calculate these goals and beam theory was used for the structural analysis to investigate whether the hollow timber blades could withstand the aerodynamic and centrifugal forces. A combination of the goals formed the objective function and a genetic algorithm (GA) was used to find a blade whose output power at a predetermined tip speed ratio (TSR) and the starting performance were high while the stress limit was met. The results show that hollow blades have starting times shorter than solid ones by approximately 70%. However, in the presence of generator resistive torque, the algorithm could not find a blade for an altitude of 3000 m. To solve that problem, the tip speed ratio was added to other design variables and another optimization was done which led to the optimal blades for both altitudes.

In the present research, we tried to improve the performance of the lattice Boltzmann (LB) -based adjoint approach by utilizing the mesoscopic inherent of the LB method. In this regard, two macroscopic discrete adjoint (MADA) and microscopic discrete adjoint (MIDA) approaches are used to answer the following two challenging questions. Is it possible to extend the concept of the macroscopic and microscopic variables of the flow field to the corresponding adjoint ones? Further, similar to the conservative laws in the LB method, is it possible to find the comparable conservation equations in the adjoint approach? If so, then a definite framework, similar to that used in the flow solution by the LB method, can be employed in the flow sensitivity analysis by the MIDA approach. This achievement can decrease the implementation cost and coding efforts of the MIDA method in complicated sensitivity analysis problems. First, the MADA and MIDA equations are extracted based on the LB method using the duality viewpoint. Meanwhile, using an elementary case, inverse design of a two-dimensional unsteady Poiseuille flow in a periodic channel with constant body forces, the procedure of analytical evaluation of the adjoint variables is described. The numerical results show that similar correlations between the distribution functions can be seen between the corresponding adjoint ones. Besides, the results are promising, emphasizing the flow field adjoint variables can be evaluated via the adjoint distribution functions. Finally, the adjoint conservative laws are introduced.

To activate the boundary layer in Active Flow Control (AFC) applications, the use of pulsating flow has notable energy advantages over constant blowing/suction jet injections. For a given AFC application, five parameters, jet location and width, inclination angle, frequency of injection, and the momentum coefficient, need to be tuned. Presently, two main devices are capable of injecting pulsating flow with a momentum coefficient sufficient to delay the boundary layer separation: these are zero-net-mass-flow Actuators (ZNMFAs) and fluidic oscillators (FOs). In the present study, a novel FO configuration is analyzed for the first time at relatively high Reynolds numbers, and fluid is considered to be incompressible. After obtaining the typical linear correlation between the incoming Reynolds number and the outlet flow oscillating frequency, the effects of dimensional modifications on outlet width and mixing chamber wedge inclination angle are addressed. Modifications of the outlet width were observed to create large variations in FO performance. The origin of self-sustained oscillations is also analyzed in the present manuscript and greatly helps in clarifying the forces acting on the jet inside the mixing chamber. In fact, we can conclude by saying that the current FO configuration is pressure-driven, although the mass flow forces appear to be much more relevant than in previously studied FO configurations.