How Does A V-N Diagram Of An Aircraft Flight Envelope?

The V-n diagram usually focuses on both positive and negative loads, however since there is little knowledge known about the box wing, for simplicity, the positive loads are assumed to be more significant. Hence, if the box wings are optimised with the positive loads, the negative loadings will also be covered due to its least significance. The 3.5g pull out of dive is known as the most extreme load which is closest to critical pressures for distortion, as shown in figure (3.4). Hence using this loading, the aircraft will be in the safe region from distortion during a flight. Figure 3.4. A V-n diagram of an aircraft flight envelope (Bill, 2009). The transient flow analysis was performed over the box wing assuming that the aircraft was pulling
The box wing Aircraft fuselage was assigned as a non-design space along with the wetted surface of the wing and the inner structure of the wing was assigned as design space. A mesh was then assigned to each component independently. A surface mesh was generated for the wing representing the wetted surface, using the same size element, as described in Chapter 3, which had converged during the CDF simulation, shown in figure (3.3). This is to gain high accuracy during topology optimisation and to match the same accuracy of the pressure gained from the surface used in the CFD simulation. The surface mesh was then used to generate a matching three-dimensional (3-D) finite volume tetra-element mesh for the internal structure (design space) of the wings. The fuselage was meshed using a moderate size 3-D volume tetra-element mesh to ensure the computation time is moderate and the computer has enough memory to perform the optimisation. The surface mesh was assigned as a non-design space representing the outer surface of a wing with 2mm thickness and the 3-D volume tetra-mesh was assigned as the internal design space, as shown in figure (4.3). The material that was chosen for the topology optimisation was Aluminium, which is usually used in the aerospace industry for structural purposes of the aircraft. The properties of the aluminium were; modulus of elasticity of 70GPa, 0.33 as Poisson’s ratio, and density of 2800kg/m3. Figure 4.1. This figure depicts the different meshing of the surfaces and solids of the box wing