The aerodynamic interaction between the contralateral wings and between the body and wings of a model insect are studied, by using the method of numerically solving the Navier-Stokes equations over moving overset grid...The aerodynamic interaction between the contralateral wings and between the body and wings of a model insect are studied, by using the method of numerically solving the Navier-Stokes equations over moving overset grids, under typical hovering and forward flight conditions. Both the interaction between the contralateral wings and the interaction between the body and wings are very weak, e.g. at hovering, changes in aerodynamic forces of a wing due to the present of the other wing are less than 3% and changes in aerodynamic forces of the wings due to presence of the body are less than 2%. The reason for this is as following. During each down- or up-stroke, a wing produces a vortex ring, which induces a relatively large jet-like flow inside the ring but very small flow outside the ring. The vortex rings of the left and right wings are on the two sides of the body. Thus one wing is outside vortex ring of the other wing and the body is outside the vortex rings of the left and right wings, resulting in the weak interactions.展开更多
In this paper, we study the aerodynamic interactions between the contralateral wings and between the body and wings of a model insect, when the insect is hovering and has various translational and rotational motions, ...In this paper, we study the aerodynamic interactions between the contralateral wings and between the body and wings of a model insect, when the insect is hovering and has various translational and rotational motions, using the method numerically solving the Navier-Stokes equations over moving overset grids. The aerodynamic interactional effects are identified by compar-ing the results of a complete model insect, the corresponding wing pair, single wing and body without the wings. Horizontal, vertical and lateral translations and roll, pitch and yaw rotations at small speeds are considered. The results indicate that for the motions considered, both the interaction between the contralateral wings and the interaction between the body and wings are weak. The changes in the forces and moments of a wing due to the contralateral wing interaction, of the wings due to the pres-ence of the body, and of the body due to the presence of the wings are generally less than 4.5%. Results show that aerodynamic forces of wings and body can be measured or computed separately in the analysis of flight stability and control of hovering in-sects.展开更多
To compute transonic flows over a complex 3D aircraft configuration, a viscous/inviscid interaction method is developed by coupling an integral boundary-layer solver with an Eluer solver in a ＂semi-inverse＂ manner. ...To compute transonic flows over a complex 3D aircraft configuration, a viscous/inviscid interaction method is developed by coupling an integral boundary-layer solver with an Eluer solver in a ＂semi-inverse＂ manner. For the turbulent boundary-layer, an integral method using Green＇s lag equation is coupled with the outer inviscid flow. A blowing velocity approach is used to simulate the displacement effects of the boundary layer. To predict the aerodynamic drag, it is developed a numerical technique called far-field method that is based on the momentum theorem, in which the total drag is divided into three component drags, i.e. viscous, induced and wave-formed. Consequently, it can provide more physical insight into the drag sources than the often-used surface integral technique. The drag decomposition can be achieved with help of the second law of thermodynamics, which implies that entropy increases and total pressure decreases only across shock wave along a streamline of an inviscid non-isentropic flow. This method has been applied to the DLR-F4 wing/body configuration showing results in good agreement with the wind tunnel data.展开更多
The aerodynamic interactions between the body and the wings of a model insect in forward flight and maneuvers are studied using the method of numerically solving the Navier-Stokes equations over moving overset grids. ...The aerodynamic interactions between the body and the wings of a model insect in forward flight and maneuvers are studied using the method of numerically solving the Navier-Stokes equations over moving overset grids. Three cases are con- sidered, including a complete insect, wing pair only and body only. By comparing the results of these cases, the interaction effect between the body and the wing pair can be identified. The changes in the force and moment coefficients of the wing pair due to the presence of the body are less than 4.5% of the mean vertical force coefficient of the model insect; the changes in the aero- dynamic force coefficients of the body due to the presence of the wings are less than 5.0% of the mean vertical force coefficient of the model insect. The results of this paper indicate that in studying the aerodynamics and flight dynamics of a flapping insect in forward flight or maneuver, separately computing （or measuring） the aerodynamic forces and moments on the wing paig and on the body could be a good approximation.展开更多
基金supported by the National Natural Science Foundation of China(10732030)the 111 Project (B 07009)
文摘The aerodynamic interaction between the contralateral wings and between the body and wings of a model insect are studied, by using the method of numerically solving the Navier-Stokes equations over moving overset grids, under typical hovering and forward flight conditions. Both the interaction between the contralateral wings and the interaction between the body and wings are very weak, e.g. at hovering, changes in aerodynamic forces of a wing due to the present of the other wing are less than 3% and changes in aerodynamic forces of the wings due to presence of the body are less than 2%. The reason for this is as following. During each down- or up-stroke, a wing produces a vortex ring, which induces a relatively large jet-like flow inside the ring but very small flow outside the ring. The vortex rings of the left and right wings are on the two sides of the body. Thus one wing is outside vortex ring of the other wing and the body is outside the vortex rings of the left and right wings, resulting in the weak interactions.
基金National Natural Science Foundation of China (10732030)"111" Project (B07009)
文摘In this paper, we study the aerodynamic interactions between the contralateral wings and between the body and wings of a model insect, when the insect is hovering and has various translational and rotational motions, using the method numerically solving the Navier-Stokes equations over moving overset grids. The aerodynamic interactional effects are identified by compar-ing the results of a complete model insect, the corresponding wing pair, single wing and body without the wings. Horizontal, vertical and lateral translations and roll, pitch and yaw rotations at small speeds are considered. The results indicate that for the motions considered, both the interaction between the contralateral wings and the interaction between the body and wings are weak. The changes in the forces and moments of a wing due to the contralateral wing interaction, of the wings due to the pres-ence of the body, and of the body due to the presence of the wings are generally less than 4.5%. Results show that aerodynamic forces of wings and body can be measured or computed separately in the analysis of flight stability and control of hovering in-sects.
文摘To compute transonic flows over a complex 3D aircraft configuration, a viscous/inviscid interaction method is developed by coupling an integral boundary-layer solver with an Eluer solver in a ＂semi-inverse＂ manner. For the turbulent boundary-layer, an integral method using Green＇s lag equation is coupled with the outer inviscid flow. A blowing velocity approach is used to simulate the displacement effects of the boundary layer. To predict the aerodynamic drag, it is developed a numerical technique called far-field method that is based on the momentum theorem, in which the total drag is divided into three component drags, i.e. viscous, induced and wave-formed. Consequently, it can provide more physical insight into the drag sources than the often-used surface integral technique. The drag decomposition can be achieved with help of the second law of thermodynamics, which implies that entropy increases and total pressure decreases only across shock wave along a streamline of an inviscid non-isentropic flow. This method has been applied to the DLR-F4 wing/body configuration showing results in good agreement with the wind tunnel data.
文摘The aerodynamic interactions between the body and the wings of a model insect in forward flight and maneuvers are studied using the method of numerically solving the Navier-Stokes equations over moving overset grids. Three cases are con- sidered, including a complete insect, wing pair only and body only. By comparing the results of these cases, the interaction effect between the body and the wing pair can be identified. The changes in the force and moment coefficients of the wing pair due to the presence of the body are less than 4.5% of the mean vertical force coefficient of the model insect; the changes in the aero- dynamic force coefficients of the body due to the presence of the wings are less than 5.0% of the mean vertical force coefficient of the model insect. The results of this paper indicate that in studying the aerodynamics and flight dynamics of a flapping insect in forward flight or maneuver, separately computing （or measuring） the aerodynamic forces and moments on the wing paig and on the body could be a good approximation.
