Low Reynolds Number Numerical Simulation of the Aerodynamic Coefficients of a 3D Wing

A low Reynolds number, three-dimensional CFD analysis is carried out for a finite flat plate wing using the commercial CFD code STAR CCM+. The six-aerodynamic force and moment components CL, CD, CM, CN, Cl, CY and their derivatives are computed at a Reynolds numbers of 3x105 by varying the pitch, roll and yaw angles about the quarter chord point. The computed results have been validated with experimental aerodynamic balance data when possible. The results indicate that roll and yaw angle affect the aerodynamic coefficients of the flat plate wing along with the pitch angle. The influence of roll and yaw angles on the six aerodynamics coefficients were found to be significant for high pitch angles specially 100 and 150. Stability derivatives have also been reported. This data is important for the design of MAVs and small UAVs and is currently perhaps not available in the open literature

Current trends in undergraduate medical and dental research: a picture from Pakistan

Abstract BACKGROUND: Initiatives taken over the last few years have led us to the day when most of the medical and dental institutions in the developed countries have established a strong research culture at undergraduate level but the situation is quite the contrary in Pakistan. This study was carried out to investigate the current trends in undergraduate medical and dental research and to highlight the research barriers. METHODS: A cross-sectional study was conducted at six medical and dental colleges of Rawalpindi and Islamabad. A structured questionnaire was used to collect data from 300 students. Results were recorded as percentages. Findings of current survey were compared with those of already reported in literature using chi-square test. RESULTS: Out of 300 students, 206 (68.7%) students had already participated in research as principal researcher, co-researcher or as a research volunteer. Internet was most effective method of publicity of research opportunities reported by 74% of students. Only 36.7% students reported the presence of student research office at their institute. Accessibility to medical and dental journals and availability of research funds were reported by 77.2% and 13.4% of students, respectively. Lack of funding and academic overload were two main research barriers reported by 92.6% and 91.9% of students, respectively. CONCLUSION: The fraction of medical and dental students who are confident that they can plan, conduct and write a research study has increased over last four years. There is an improvement in the availability of research promoting activities but the number of research barriers is still hi

A numerical investigation of explicit pressure-correction projection methods for incompressible flows

A numerical investigation is performed on an explicit pressure-correction projection method. The schemes are fully explicit in time in the framework of the finite difference method. They are tested on benchmark cases of a lid-driven cavity flow, flow past a cylinder and flow over a backward facing step. Comparisons of the numerical simulations have been made with benchmark experimental and DNS data. Based on the results obtained, several numerical issues are discussed; namely, the handling of the pressure term, time discretization and spatial discretization of convective and diffusive terms. The fully explicit projection method is also compared with the fully implicit SIMPLE algorithm. It is observed that the SIMPLE algorithm performs better (faster and produces more accurate results) for laminar flows while the projection method works better for unsteady turbulent flows. Although there have been much research performed using the higher-order pressure incremental projection method, this research work is novel because the schemes employed here are fully explicit, developed in the framework of a finite difference method, and applied to turbulent flows using k- model. The major difficulty and challenges of this research work is to identify the sources of instability for the higher-order pressure incremental projection method scheme

Passive drag reduction of square back road vehicles

Bluff body vehicles such as trucks and buses do not have a streamlined shapes and hence have high drag which can be reduced to make great savings in operational cost. While rectangular flaps have been widely studied as both passive add-ons and in active drag reducing systems for bluff bodies, changing the basic geometry of the flap has not been explored in literature. In this work, a baseline drag value is obtained for a simplified MAN TGX series truck in a CFD software, and the drag reduction of a proposed elliptically shaped flap is compared to aerodynamically equivalent rectangular flaps. The optimal mounting angle for both flaps is found to be 501. A parametric study of changing the ellipse semi-major axis is carried out to find the optimal length for drag reduction. A maximum drag reduction of 11.1% is achieved using an elliptical flap with 0.12 m semi-major axis; compared to 6.37% for a length equivalent rectangular flap, and 6.84% for a surface area equivalent rectangular flap. Results of the pressure distribution and velocity flow behind the rear of the truck are also given and analyzed

Active control of base pressure with counter clockwise rotating cylinder at Mach 2

The effect of dynamic cylinder as an active controller to control the base pressure for different level of expansion have been experimentally investigated at Mach 2 through CD nozzle for area ratio 9. Solitary counter clockwise rotating cylinder of 2 mm diameter when seen from top, at 2 mm from side wall of square duct and 8 mm from square nozzle exit in the base region is mounted as a controller. Base pressure in the wake area after sudden expansion of jets from the exit of nozzle has been measured. The length-to-width ratio of sudden expansion duct taken is 10. The experiments were carried out by operating jets for different nozzle pressure ratios (NPR). The wall pressure distribution was also measured for with and without control cases in the duct to see that the amplitude of oscillations does not adversely influence the flow field in the duct. Counter clockwise rotating cylinder as an active controller were found to increase the base pressure as high as 62 percent at NPR 8.5 and 53 percent at NPR 7.8. The control effectiveness is marginal for over expanded nozzles. The wall pressure flow field with and without control are identical with minor fluctuations

Literature Review: Biomimetic and Conventional Aircraft Wing Tips

This paper is an attempt to summarize the effect of wing tip devices employed by birds, as well as aeronautical engineers in the past to improve the performance characteristics of aircraft. The focus is on reduction of the induced drag or drag due to lift also known as inviscid drag. This paper will provide an insight on both biomimetic and conventional wing tip approaches to reduce the induced drag. Prior analysis and experiments on the aerodynamics of airplane performance due to both these separate studies have been discussed. The needs of the industry and their past inventions have been described briefly as well as new areas to be explored have been highlighted. NOTE: This article is not peer reviewed

Flowfield-dependent variant method for moving-boundary problems

A novel numerical scheme using the combination of flowfield-dependent variation method and arbitrary Lagrangian–Eulerian method is developed. This method is a mixed explicit–implicit numerical scheme, and its implicitness is dependent on the physical properties of the flowfield. The scheme is discretized using the finite-volume method to give flexibility in dealing with complicated geometries. The formulation itself yields a sparse matrix, which can be solved by using any iterative algorithm. Several benchmark problems in two-dimensional inviscid and viscous flow have been selected to validate the method. Good agreement with available experimental and numerical data in the literature has been obtained, thus showing its promising application in complex fluid–structure interaction problems