Drag performance of divergent tubular-truncated cones: a shape optimization study

Abstract

The use of more efficient energy consuming devices, which are closely associated with reduction of environmental pollution, has gained significant interest in the recent decades. The reduction of drag coefficient also improves safety and durability of environmental structures subjected to high-velocity fluid flow, and causes the noise and vibration to decrease as well. This paper describes the efficiency improvement in energy management by means of reducing drag coefficient in a practical divergent tubular-truncated cone. Extensive numerical simulations with emphasis on the shape optimization study were performed in order to find minimum drag coefficient for both laminar and turbulent flows (9.41 9 10 2 B Re B 1.882 9 10 7 ) around the mentioned cone. The numerical results were validated with experimental data, obtained by performing tests in an open circuit wind tunnel. The results showed that the minimum drag coefficient of optimum model within the shape modification process, comparable to the value for the primary model in turbulent flow decreased by 69.8% (the maximum discrepancy) at the highest considered Reynolds number of 1.882 9 10 7 . Furthermore, the study of streamwise velocity profile led to more useful result. In this regard, the velocity magnitude inside the inlet span of the primary model, close to the entrance was approximately 1.6 times as great as the free upstream velocity. This is a noticeable result for the use of efficiency important structures in industrial applications.

Conceptual duct shape design for horizontal-axis hydrokinetic turbines

“…Experimentally measured drag forces for smooth and rough tubular frustum were reported in [25]. Results of similar experiments for tubular-truncated cones were reported in [26]. These data can be employed to validate the numerical solution method used for predictions of duct drag coe cient.…”

“…The ow Reynolds number used in the numerical simulations is Re D = 2:25 10 6 , which was computed based on the duct throat diameter. In the experiments of reference [26], the ow direction is parallel to the tubular cone axis and the smaller area is faced with the ow direction such that tubular cone acts as a di user. For a suitable comparison, the experimentally measured drag forces were non-dimensioned based on the frontal cross sectional area (smallest ow passage area).…”

“…In this case, the drag coe cients for smooth and rough tubular cones (with mean roughness of 1.5 mm) were 3.41 and 3.62, respectively. These values were recalculated from data in [25,26]. The numerical prediction of drag coe cient for Model 4-A with smooth walls is 3.42.…”

Review on Diffuser Augmented Wind Turbine (DAWT)

“…The simulation result showed that maximum increases of upstream wind velocity was obtained by model T which was about 60%. Thus the possibility of using model T in energy production system to bring with it an advantage of the increase in wind speed [80]. Depending upon the analytical study included an optimized configuration of a Ducted Wind Turbine with ejector type assist for the exhaust (Fig.17), may getting Power Coefficients up to 0.6.…”

“…This corresponds to the output of nearly 15 conventional unducted wind Turbines (with a typical CP=0.4) where numerical simulation in two dimensional by CFD used to investigate that [81]. Table 1 Primary and modified models of tubular divergent-truncated cone [80]. Fig.…”