Jhon Nero Vaz Goulart

Constructal Design Applied to a Channel with Triangular Fins Submitted to Forced Convection

The purpose of this work is to present a numerical study of a two-dimensional channel with two triangular fins submitted to a laminar flow with forced convection heat transfer, evaluating the geometry of the first fin through the Constructal Design method. The main objectives are to maximize the heat transfer rate and minimize the pressure difference between the inlet and outlet flow of the channel for different dimensions of the first channel fin, considering the same Reynolds (ReH = 100) and Prandtl numbers (Pr = 0.71). The problem is subjected to three constraints given by the channel area, fin area and maximum occupancy area of each fin. The system has three degrees of freedom. The first is given by the ratio between height and length of the channel, which is kept fixed, H/L = 0.0625. The other two are the ratio between height and width of the upstream fin base (H3/L3) positioned on the lower surface of the channel, and the ratio between height and width of the downstream fin (H4/L4) positioned on the upper surface of the channel, which is also kept fixed, H4/L4 = 1.11. The problem is simulated for three different values of the fraction area of upstream fin (φ1 = 0.1, 0.2 and 0.3). For the numerical approach of the problem, the conservation equations of mass, momentum and energy are solved using the finite volume method (MVF). The results showed that a ratio of φ1 = 0.2 is the one that best meets the proposed multi-objective. It was also observed that φ1 = 0.1 led to a better fluid dynamics performance with a ratio between the best and the worst performance for fluid dynamics case of 25.2 times. For φ1 = 0.3, the best thermal performance is achieved, where the optimal case has a performance 65.75% higher than that reached for the worst case.

A Numerical Study of the Turbulent Flow over a Cylinder close to Moving Plane

Two-dimensional numerical simulations are performed to analyze the turbulent flow over a circular cylinder close to a moving plane. This flow receives interference from the plane boundary layer, being this effect identified by recirculation zones close to the wall and slight difference in pressure distribution around cylinder. URANS equations and SST modeling are employed to calculate velocity and pressure field. The simulation was performed by a finite element projection scheme. Four distances between the cylinder and the plane are analyzed by the SST model. The SST results showed the generation and development of vortex shedding. Lift and drag coefficients show the flow oscillatory pattern. All results are similar with other numerical results at the literature.

Using URANS to Predict Turbulent Flow Features in a Channel with Lateral Slot

Employing a commercial code an unsteady Reynolds Average Navier-Stokes (URANS) with Spalart-Allmaras as turbulence model numerical calculations were performed in order to predict the mean and velocity fluctuations fields in a rectangular channel with a lateral slot. The slot is attached to a lateral wall channel, being characterized by its deepness p and the gap width d. Simulations were performed keeping constant the slot deepness p and the length L while the gap width d was increased from 2 up to 6 mm. Three test sections involving p/d ratios12.50, 6.25 and 4.17were studied. Main results revealed that turbulence production increases with gap dimension decreasing. Large scale structures appearance were also the target of this paper. The study showed gap width plays an important role on this issue. As the gap width was increased large scales structures could be observed farther from channels entrance. Moreover, a kind of viscous effect in the gap was observed. As gap become very tight the frequency of coherent motions is reduced.