Transonic Aerodynamic Performance Analysis of a CRM Joined-Wing Configuration

This study examines the aerodynamic performance of a joined-wing (JW) aircraft design based on the NASA Common Research Model (CRM), aiming to assess its potential for efficient commercial transport or cargo aircraft at transonic speed (Mach 0.85). The CRM wing, optimised for transonic flight, was transformed into a JW design featuring a high-aspect-ratio main wing. An initial parametric study using the vortex lattice minimum drag panel method identified viable designs. The selected JW configuration, comprising front and rear wings joined by a vertical fin, was analysed using ANSYS Fluent to understand flow interactions and aerodynamic performance. At an angle of attack (AoA) of -1 degrees, the JW design achieved a peak lift-to-drag ratio (L/D) of 17.45, close to the CRM's peak L/D of 19.64 at 2 degrees, demonstrating competitive efficiency. The JW's L/D exceeded the CRM's between AoA -3 degrees and 0.8 degrees, but the CRM performed better above 0.8 degrees, with differences decreasing at a higher AoA. Based on induced drag alone, the JW outperformed the CRM across AoA -3 degrees to 8 degrees, but flow complications restricted its L/D advantage to a small, low AoA range. A strong shock on the vertical fin's inboard side due to high incoming flow speed delayed shock formation on the main wing near the joint. Optimising the vertical fin shape slightly improved L/D, suggesting potential for further enhancements or that other design factors significantly affect JW performance. This study provides insights into JW aerodynamics at transonic speeds, revealing its potential benefits and challenges compared to the CRM design.