Investigation of a Light Boxplane Model Using Tuft Flow Visualization and CFD

In this paper, we addressed the flow patterns over a light boxplane scale model to explain the previously discovered disagreement between its predicted and experimental aerodynamic characteristics. By tuft flow and CFD visualization, we explored the causes yielding a large zero lift pitching moment coefficient, lateral divergence, difference in fore and aft elevator lift, and poor high lift performance of the aircraft. The investigation revealed that the discrepancy in the pitching moment coefficient and lateral stability derivatives can be attributed to insufficient accuracy of the used predictive methods. The difference in fore and aft elevator lift and poor high lift performance of the aircraft may occur due to the low local Reynolds number, which causes the early flow separation over the elevators and flaperons when deflected downward at angles exceeding 10°. Additionally, some airframe changes are suggested to alleviate the lateral divergence of the model.

Numerical investigations of vortex formation on a generic multiple-swept-wing configuration

For an improvement of the flight stability characteristics of high-agility aircraft, the comprehension of the vortex development, behavior and break down is important. Therefore, numerical investigations on low aspect ratio, multiple-swept-wing configurations are performed in this study to analyze the influence of the numerical method on the vortex formation. The discussed configurations are based on a triple- and double-delta wing planform. Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations and delayed detached eddy simulations (DDES) are performed for both configurations. The simulations are executed at Re $$= 3.0\times 10^6$$ = 3.0 × 10 6 , symmetric freestream conditions, and an angle of attack of $$\alpha = 16^\circ$$ α = 16 ∘ , for consistency with reference wind tunnel data. For the triple-delta-wing configuration, the results of the DDES show a satisfying accordance to the experiments compared to URANS, especially for the flow field and the pitching moment coefficient. For the double-delta-wing configuration, the URANS simulation provides reliable results with low deviation of the aerodynamic coefficients and high precision for the flow field development with respect to the experimental data.

Aeroelastic simulations of a delta wing with a Chimera approach for deflected control surfaces

A numerical tool for the computation of aircraft control surface aerodynamics with flexibility effects is presented. The solution is based on coupled Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM) simulations embedded in the multidisciplinary simulation environment SimServer. In SimServer, the DLR-TAU Code is utilized to obtain the CFD solution by solving the Reynolds-Averaged Navier–Stokes (RANS) equations. Structural displacements are computed with a modal solver. The Chimera implementation of SimServer, suited for hybrid grids, is applied to model the control surfaces. Numerical simulations with the flexible Chimera method are performed for the Model53 wing configuration, which is a generic delta wing with a deployed slat as well as an inboard and outboard trailing edge flap. Aerodynamic and aeroelastic simulations at high dynamic pressure $$q=45$$ q = 45 kPa and transonic speed $${\text {Ma}} = 0.8$$ Ma = 0.8 are performed for several angles of attack $$10^\circ \le \alpha \le 25^\circ$$ 10 ∘ ≤ α ≤ 25 ∘ and flap deflection angles $$-30^\circ \le \delta \le 30^\circ$$ - 30 ∘ ≤ δ ≤ 30 ∘ . The effect of structural deformations on the flow field and control surface effectiveness are analyzed and compared to computations of components treated fully rigid. At the targeted freestream condition $$M=0.8$$ M = 0.8 and $${\text {Re}}=15.1 \times 10^7$$ Re = 15.1 × 10 7 , the flow field around the Model53 configuration is characterized by the interaction of vortices and shock waves. The results of the lift and pitching moment coefficient for the rigid and flexible configuration revealed the importance of taking the structural flexibility into account in order to obtain more accurate results for the considered range of flap deflections. Furthermore, the computational effort of the aerodynamic and aeroelastic simulations are evaluated. The increase in computational effort is shown to be adequate for the given increase in accuracy.

How is economic growth correlated to index growth?

This study will mainly focus on the relation between GDP growth and stock market index growth through various methods like the Pearson product-moment coefficient correlation, comparing the theoretical world to the real-world situation, and finally by looking at consumer sentiments and confidence. This could help various analysts, economists, and even the general public. Through the course of our study, we find out various trends in this study, at some point, the results were contradicting themselves but then our last test made it all clear, which proves that there is no correlation between GDP growth and stock market index growth, but then both of them drives from consumer confidence and consumers future actions.

Desain Underwater Rotor Untuk Memanfaatkan Laju Aliran Sungai Sebagai Pembangkit Listrik Tenaga Air

<p><em>This study aims to design an underwater rotor to utilize the flow rate of the river as a hydroelectric power plant. In this study, an underwater rotor design model will be made with three variations in the number of blades, namely three, six, nine blades. The test parameter observed in this study is the turbine performance through the value of the power coefficient (cp) and the moment coefficient (cm). The method used in this research is an experimental method, namely by making a turbine model with a laboratory scale. The results show that the underwater rotor designed with aspect ratio = 2.0, overlap ratio = 0, end-plate diameter = 1.1d then the barrier plate design with L/D ratio = 1.2 60º provides the highest power coefficient and moment coefficient, namely respectively 0.15 and 0.27 in the design with the number of blades 3 (three)</em></p>

Competitive Intelligence and Resilience of Small Medium Enterprises (SMEs) in Developing Economies

Small and Medium Enterprises SMEs hold the key to economic progress and development in developing economies including Nigeria. This study therefore examined the effect of competitive intelligence on the survival of SMEs in Benin City, Edo State, Nigeria. To achieve these objectives three hypotheses were formulated to establish whether or not there is a relationship existing between the two intervening variable i.e. competitive intelligence and the survival of SMEs in Benin City, Edo State and by extension Nigeria. Survey research design was adopted, while data were obtained from structured questionnaire and analyzed using Pearson’s product-moment coefficient of correlation. From the analysis, the results indicated that there is an existing relationship between the variables. Based on the findings it was concluded that for SMEs to survive and expand its market frontiers in the face of the escalating competition in the business environment, there is the need to take a holistic view of their strategies and offer innovative products that can provide customers with valued and satisfying benefits better than the ones offered by competitors and engaging in superior marketing strategies to enhance performance and productivity. The study recommended among others that SMEs should identify and prune down unwarranted business expenses without necessarily impacting negatively on the operations of the firm. Keywords: Innovative Products, Performance, Productivity, Satisfying Benefits, SMEs, Survival.

Low Reynolds Number Scaling Eeffects For Small-Scale Rotors

<div>Three T-Motor rotors with different diameters but otherwise identical relative geometries were tested in fully edgewise flow at different advance ratios and Reynolds numbers. The objective was to verify whether the existing scaling relationships between rotor size and the aerodynamic forces are applicable to small scale rotors that operate at relatively low chord-Reynolds numbers. The rotors were mounted onto a test stand housed inside a closed loop wind-tunnel where the air speed of the tunnel was varied to achieve different advance ratios. The chord-Reynolds umber at 75% of the radius of each blade were matched for ranges from 39,000 to 117,000. The experimental data was also compared to computational results from a blade element momentum theory-based method. The results showed that the existing coefficient based scaling laws can be used to predict the performance parameters for the thrust coefficient, power coefficient, longitudinal force coefficient, side force coefficient and, rolling moment coefficient for the full range of Reynolds numbers tested. Although for the pitching moment coefficient, a coefficient approach became less applicable for chord-Reynolds number of less than 100,000.</div>

Low Reynolds Number Scaling Eeffects For Small-Scale Rotors

<div>Three T-Motor rotors with different diameters but otherwise identical relative geometries were tested in fully edgewise flow at different advance ratios and Reynolds numbers. The objective was to verify whether the existing scaling relationships between rotor size and the aerodynamic forces are applicable to small scale rotors that operate at relatively low chord-Reynolds numbers. The rotors were mounted onto a test stand housed inside a closed loop wind-tunnel where the air speed of the tunnel was varied to achieve different advance ratios. The chord-Reynolds umber at 75% of the radius of each blade were matched for ranges from 39,000 to 117,000. The experimental data was also compared to computational results from a blade element momentum theory-based method. The results showed that the existing coefficient based scaling laws can be used to predict the performance parameters for the thrust coefficient, power coefficient, longitudinal force coefficient, side force coefficient and, rolling moment coefficient for the full range of Reynolds numbers tested. Although for the pitching moment coefficient, a coefficient approach became less applicable for chord-Reynolds number of less than 100,000.</div>

AIR-BT, a new badminton-specific incremental easy-to-use test

Background Badminton is a highly demanding sport characterized by intermittent efforts with energy being provided by both the aerobic and anaerobic systems. To date, no incremental badminton field test has been developed that can be easily used by badminton coaches that requires accessible material for anyone. Objectives The purpose of this study was to develop a practical and reliable easy-to use intermittent endurance badminton test for estimating maximal oxygen uptake (VO2max). Methods Thirty six Spanish badminton players (age: 24.1±10.3 years) performed, on different days of the same week, four incremental protocols to exhaustion in randomized order: a treadmill incremental test, a Yo-Yo intermittent recovery level 1 test (Yo-Yo IR1) and twice the Abian intermittent recovery badminton test (AIR-BT). Oxygen uptake was determined with a breath-by-breath gas analyzer during the incremental treadmill test, and performance in the Yo-yo IR1 and AIR-BT was recorded. Results Significant correlations (p<0.001) for Pearson’s product moment coefficient were found between the performance in the AIR-BT and the two non-specific incremental tests (VO2max in the Treadmill Test: r = 0.87, distance in the Yo-Yo IR1: r = 0.86). The regression equation to calculate the VO2max from the AIR-BT time [VO2max = 0.023*(AIR-BT time in seconds)+31.334] showed an adjusted R2 of 0.76 and a SEE of 3.34 ml·kg-1·min-1. There was no significant difference between VO2max obtained by the incremental treadmill test and VO2max calculated using the regression equation (p = 0.644). A paired t-test reported no significant differences between day 1 and day 2 in the AIR-BT time (p = 0.753), the Pearson correlation coefficient between both days was: r = 0.88 (p<0.001) and the intraclass correlation coefficient was 0.875. Conclusions The AIR-BT is a valid and reliable on-court test for assessing VO2max in badminton players and may be utilized by coaches and physical trainers for cross-sectional comparison of players and for evaluation of longitudinal changes.

Parametric sensitivity research of interference-fit bolted single-lap laminates joint based on an improved analytical stiffness model

Because of the excellent static and fatigue performance, the interference-fit bolted structure has a wide application prospect in the joint field. In this paper, an improved spring-mass stiffness analytical prediction model is established for the interference-fit bolted single-lap laminated composite structure. The influences of interference-fit percentage, bolt preload, secondary bending and interface frictions are considered in the model. Combined with experimental research, the value of secondary bending moment coefficient ε is studied, and the correctness of the analytical model is verified. Based on the improved stiffness model, parametric research and regression analysis on the interference-fit percentage, preload, friction, laminate width and material properties are carried out and show that the overall structure stiffness is obviously affected by ε value, laminate width and laminates properties. The stiffness decreases with the increase of ε and increases with the increase of laminate width. And as the key factors, the interference-fit percentage mainly affects the joint local friction and bolt shear stiffness, the preload and friction coefficient mainly affect the local friction, and the laminates sizes and properties directly affect the overall structural stiffness.