Experimental study on the effect of bionic flap parameters on airfoil aerodynamic performance

The effects of bionic flap on airfoil performance were experimentally studied to provide theoretical support for the application of the bionic flap in aeronautical engineering. Seven kinds of bionic flaps were used to study the effects of the key flap parameters, including the flap angle, length, shape, and position, at a Reynolds number of Re = 0.8 × 106. At small angle of attacks (AoAs), the drag and pitching moment increased and the lift reduced when using the bionic flap. While at high AoAs, the lift increased and the drag reduced, which improved the airfoil stall characteristics. The configuration of deflection bionic flap had the smallest initial AoA for improving the airfoil stall characteristics in the seven kinds of bionic flaps. More than eight degrees of the effective AoA range for improving lift characteristics could be achieved. The maximum lift coefficient could be increased by 3.9%. Additionally, the control mechanisms of the flap under different flow conditions (attached flow and separated flow) were deeply studied. In the attached flow, the effective camber and thickness of the basic airfoil could be changed by the flap, resulting that the flow around the airfoil was affected, which in turn affected the Cl and the slope of the lift line. In the separated flow, the flap affected the flow around the airfoil by controlling the development of the trailing edge separation vortex. These research results confirmed the aerodynamic mechanisms for the formation of double layered feathers when birds land, and provided insight into application of bionic flaps in aeronautical engineering.

Transonic Static Aeroelastic Numerical Analysis of Flexible Complex Configuration Wing

Diamond back wing is subjected to large deformation while gliding, which significantly changes characteristics of the lift as well as the static stability. For this reason, conventional rigid aircraft assumption cannot meet the requirements of the aerodynamic analysis of such aircrafts for accuracy. In this paper, based on CFD/CSD methods, the static aeroelasticity of a small diameter bomb with diamond back wing was studied. The results showed that static aeroelastic effects cause the slope of lift line to drop by 21% and the aerodynamic centre to move backwards by a 1.5% bomb body length, which will deviate the actual flight performance from the design point, thereby decreasing the cruise efficiency and the cruise range.

Effect of Placement Technology on the Bond Strength Between Two Layers of Self-Compacting Concrete

Self-compacting concrete (SCC) should generally be placed continuously, but it is not uncommon for contractors to be forced to use interruptions in concrete works due to delivery delays. The multilayer casting of SCC can cause weak bond conditions in the contact area of subsequent layers. Methods of preventing cold joint or lift line formation for normal concretes are not suitable for self-compacting concretes. This article provides research on the effect of multilayer casting technology on the bond strength between two layers of SCC. Three technological variants of connecting successive layers of SCC mixture on beam elements were analyzed: The free flow of the mixture, dropping the mixture from a greater height, and mechanical disturbance of the first layer. Three delay times were applied: 30, 45, and 60 min between two layers of SCC. In general, the research revealed that, regardless of the multilayer casting variant, the bond strength between two layers decreased as the delay time was extended. The best performance and the lowest drop in bond strength were obtained for samples with a mechanically disturbed first layer, independent of the delay time. This method gave similar results to a reference element made without a break in concreting. It was also demonstrated that current recommendations and standard guidelines for multilayer casting appear to be insufficient for ensuring an adequate bond between layers.

Cartesian Versus Joint Space Command Shaping for a Ship Boom Crane

This paper presents a command shaping control method for suppressing operator induced payload swing in rotary, ship-based, boom cranes. The crane configuration studied consists of a payload mass that swings on the end of a spherical pendulum of varying lift-line length (hoisting). The lift-line is attached to a boom capable of elevation (luffing). The boom can rotate about an axis perpendicular to the ship’s deck (slewing). Positioning of the payload is accomplished through luff, slew, and hoist commands issued in real-time by an operator. A Cartesian space command shaping method is developed and compared to a previously documented joint space approach. Although both methods are appropriate for low rate crane maneuvers, the Cartesian method provides better performance under the tested operating conditions. Simulation results are presented to compare their performance.

Effect of Groove Shape on the Frictional Hold of a Sheave on Polyester Rope

This paper discusses the effects of sheave groove shape, sheave diameter, and line tension on the frictional hold of polyester rope. A series of tests were conducted using five different sheaves, 5 and 9.2-cm-dia 2-in-1 polyester rope, under both wet and dry conditions. The frictional hold was determined from the difference in rope tension on opposite sides of a rotating sheave. The maximum tension on the high side was 245 kN. It was found that the coefficient of friction between polyester rope and smooth steel sheaves decreases with increase in rope tension for a given rope size. The 70-deg-V groove sheave shape demonstrated approximately 25 percent more frictional hold than the U-groove sheave shape. Holding capacity increases with sheave diameter. Large relative velocity exists between elastic lift line and sheave surface. Data will be used in a traction winch design.