Modelling of Drag Force Reduction for a Waterjet Propulsion System

The paper provides simulation results for SUP (Stand Up Paddle) board appendage resistance. Additional propulsion is added to the SUP board. It is equipped with a waterjet. The waterjet is attached to the board rudder. This increases the drag coefficient for rudder five times. To reduce the drag variable, design options for the waterjet duct were proposed. The simulation tests were performed using SolidWorks Flow software using two types of simulations, namely, the pressure on the body and the flow around the body. The objective was to streamline the bluff duct of the waterjet and thus to create the appendage design with minimum drag force from fluid flow and possibly greater Inlet Velocity Ratio. Calculations showed that rounding-off the edges of waterjet duct resulted in 35 % of drag coefficient reduction, while further streamlining reduced it by additional 10 %.

Computational and Experimental Study for Reducing Forebody Wake Effect by Proper Designing of a Slit cut Square Parachute used for Sonobuoy Drop

This paper discusses the design of a square parachute based on classical approach, computational analysis and experimentation. This parachute will be used to drop directional sonobuoy on the sea to locate and classify the submarines. Design improvements are brought out by providing slits into a solid square canopy of parachute to bring in more stability and minimum drift during descend. Specifically, the effect of upstream sonobuoy, RANS model, suspension line length, canopy size and slit size in flow structure were considered. The predicted drag coefficients obtained from CFD for square canopy with slit-cuts compared with the results of wind tunnel experiment and found that the increase in the suspension-line length and/or of the surface area of the parachute canopy helps in better stability and results in the minimum drag loss.

The Specific Fuel Consumption of Aircraft Engines (TSFC versus PSFC)

From a fundamental consideration of the efficiency (eta = P_out / P_in) it already follows that the power-specific fuel consumption, PSFC or c_P of an aircraft engine should be approximately constant, while c = c_P * V applies to the thrust-specific fuel consumption, TSFC or c in a first approach. Obviously, fuel is consumed already at static thrust (V=0). For this reason the thrust-specific fuel consumption needs an extended approach c = c_a + c_b * V. Breguet's range equation can certainly be described with a constant thrust-specific fuel consumption c, if c is determined for the cruise speed in question. However, this leads to an error if you want to use it to calculate an optimal flight speed in a flight performance calculation. It is recommended (for a first simple consideration) to write Breguet's range equation for jets with a constant power-specific fuel consumption c_P. This then leads to an optimal cruising speed for maximum range at minimum drag (md) V_md instead of 1.316 * V_md as it is determined with the "classic" derivation. For more detailed considerations, the "Herrmann model" should replace the simple equation c = c_a + c_b * V.

Investigation of Falcon Dive and Developing Kinematic Approach

This study investigates the aerodynamic methods already implemented in studying a peregrine falcon dive. The paper presents a literature review of aerodynamic methods, starting from mathematical models aimed at predicting falcon dive using minimum drag theory. This is followed by experimental methods that developed the flight path trajectory using high-tech cameras. Additionally, the paper presents numerical analysis of the falcon body model using computational fluid dynamics and particle image velocimetry in order to assess and derive aerodynamic coefficients. Based on the research, a kinematic model for the problem was developed, and the reason for failure were highlighted.

Investigation of Falcon Dive and Developing Kinematic Approach

This study investigates the aerodynamic methods already implemented in studying a peregrine falcon dive. The paper presents a literature review of aerodynamic methods, starting from mathematical models aimed at predicting falcon dive using minimum drag theory. This is followed by experimental methods that developed the flight path trajectory using high-tech cameras. Additionally, the paper presents numerical analysis of the falcon body model using computational fluid dynamics and particle image velocimetry in order to assess and derive aerodynamic coefficients. Based on the research, a kinematic model for the problem was developed, and the reason for failure were highlighted.

Three-Surface Model with Redundant Longitudinal Control: Modeling, Trim Optimization and Control in a Preliminary Design Perspective

Notwithstanding the interest in the three-surface concept shown by aircraft designers, this configuration was not thoroughly investigated in conjunction with the adoption of two-elevator surfaces, on both canard and tail. In fact, the inclusion of an additional elevator produces a redundant longitudinal control which can be specifically exploited to target trim optimization. The same redundancy can be also employed to improve the flying qualities of the three-surface aircraft. In this paper, after introducing a simple flight mechanics model, ideal for preliminary design and analyses, the advantages of this configuration are explored. Firstly, the problem of finding the elevator deflections of canard and tail for minimum drag in trim is formulated and solved. Secondarily, the updating of a two-surface back-tailed airplane into an equivalent three-surface one is demonstrated, showing the potential improvement in cruise performance. Finally, the controls are employed through a smart control law for achieving better flying qualities.

Effect of Cutting Ratio and Catch on Drag Characteristics and Fluttering Motions of Midwater Trawl Codend

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of a midwater trawl codend. These are generally affected by catch, cutting ratio, mesh size, and twine diameter. In this study, six nylon codend models with different cutting ratios (no cutting, 6:1, 5:1, 4:1, 7:2, and 3:1) were designed and tested in a professional flume tank under two conditions (empty codends and codends with catch) and five current speeds to obtain the drag force, spatial geometry, and movement trend. As the cutting ratio of empty codends decreased, the drag force decreased, and the drag coefficient increased. The unfolding degree of codend netting and the height of empty codends were found to be directly proportional to the current speed and inversely proportional to the cutting ratio. The positional amplitude of codend with cutting ratio 4:1 was the smallest for catch. The drag force of codends with catch increased as the current speed increased, and first decreased and then increased as the cutting ratio decreased. To ensure the best stability and minimum drag force of the codend, it is recommended to use the 4:1 cutting ratio codend.

Aerodynamics Analysis on Wings with Winglets and Vortex Generators

This project was based on the principle of designing, simulating and developing an inexpensive, aerodynamically efficient and regular class electric powered RC aircraft. This prototype was designed to have the maximum strength to weight ratio with minimum drag coefficient (and highest lift coefficient). Moreover, all constraints provided by SAE International competition were followed. The investigation was conducted for the complete airplane and for wing optimization. The model was numerically investigated with ANSYS Fluent 16.1 through the SST K-Omega turbulence model at Reynolds number of 360,000. Once the results were obtained, model and result verification were done by wind tunnel test to validate the data. It was concluded that the airplane with 45° winglet has the highest lift force with minimal drag and 45° winglet was further modified with rectangular and triangular vortex generators in order to further enhance its aerodynamic efficiency for a range of Angle of Attacks (AOA).