What are the best methods and tools for estimating drag polar and lift curve slope?

In the early conceptual phase, vortex lattice methods and panel codes will be the best tools for early evaluation of aircraft polars, though they must be used in addition to tools that can calculate drag rise and/or far-field wave drag (if applicable). The temptation will be there to use CFD very early on in the design process, but this can be foolhardy as it can over-penalize a design for artifacts in early surface models that will not be there as an OML is refined and optimized. My advice would be to stick with other tools until your OML reaches a certain stage of maturity.

In the world of aerodynamics, accurately estimating drag polar and lift curve slope is crucial. From wind tunnel testing to computational fluid dynamics (CFD), the quest for precision is constant. But let's broaden our horizon - What innovative methods or tools have you encountered in this field? Together, we can chart the most efficient course through the skies of aerodynamic exploration! #Aerodynamics #Innovation #Collaboration #AviationExcellence

Depending on the stage of your design, tools and methods vary. Simplest form is calculations based on empiric formulae or statistical data from previous designs. These are suitable for the earliest phases of aircraft design (napkin sketch). Best resource for additional info is D. Raymer's 'Aircraft Design' textbook. Next step is more advanced methods, like VLM or Panel for lift and induced drag and more advanced empiric for parasitic drag, like Hoerner. My favourite tools are OpenVSP and Flow5. For more advanced stages, like final details of OML (outside mould lines), various CFD tools. These are usually combined (calibrated) with wind tunnel tests. At end of the project (post first flight), actual flight test data becomes available.

depending on your design stage you can use induced drag (with Oswald coefficient), VLM or RANS simulations to get your polar curves. The three types are available in one software named "ACE of Aircraft"

As for the drag polar, it depends on the stage of your design. The thing to keep in mind with lift is that for low AoAs, there is a multitude of tools and even the simple ones give fair estimations. Where it starts to complicate is when you get into the higher AoAs. Close to stall, various phenomena may start to develop, and here even CFD and Wind Tunnel data is not completely trustworthy. Often times, only flight tests can show actual behaviour near stall. As always in aircraft design, build up your design from simpler to more complex methods, always comparing to previous results. Trying to understand flow behaviour and imagining the impact of various oml features down the flow is key.

For the flight envelope, excel and the appropriate CS- standard is king. Of course quality data from the aerodynamic team is key!

High-Fidelity Multiphysics simulations take into account interactions between various physical phenomena, such as structural dynamics, aerodynamics & thermodynamics, to predict more accurate aerodynamic characteristics under realistic operating conditions. COMSOL Multiphysics is known for its ability to handle complex multiphysics problems, integrating structural & fluid dynamics to predict performance. In developing a high-speed military drone, multiphysics simulations were crucial. We examined how thermal effects at high speeds influenced air density around the wing surfaces, affecting lift and drag. These simulations guided the thermal protection system design to ensure aerodynamic efficiency was maintained at high speeds.

Panel methods offer an efficient approach to modeling aerodynamic flows around complex aircraft geometries. Panel methods discretize aircraft surfaces into panels and solve the potential flow equations to calculate air velocities and pressures. Tools like VSPAERO and OpenVSP employ panel methods to compute aerodynamic forces and moments, including lift and drag, for diverse aircraft configurations. By analyzing the results, engineers can estimate drag polar and lift curve slope to optimize aircraft performance. Advanced instrumentation techniques enhance the accuracy and reliability of wind tunnel tests for aerodynamic analysis.

When you design an aircraft, drag and lift are very important parameters but stability (static and dynamic) is also a key factor.