Case study
Twin-engine aircraft with crosswind
Turbostream 4 unsteady simulation of the NASA Common Research Model (CRM) at a 40-knot crosswind, start of takeoff condition.
This simulation uses the NASA Common Research Model (CRM) and NASA Stage 67 to understand the differences between two engine fans when the aircraft operates under crosswind. Turbostream 4 runs this calculation at a speed of one fan revolution per 5 hours on a modest cluster of 32 GPUs, allowing this type of calculation to be included in the fan design process.
One of the critical off-design conditions for an engine fan is at the start of takeoff with full engine power under a strong crosswind. The freestream flow is perpendicular to the engine axis, usually leading to flow separation inside the intake and ingestion of a ground vortex into the fan. These results show that the influence of the airframe creates different inlet flow fields for the two fans. Each fan ingests a ground vortex with different strengths and locations and the upwind engine has a large flow separation in the intake.
All the pre-and post-processing for this simulation was carried out in the Turbostream Processor Graphical User Interface (GUI). The aircraft domain uses an unstructured grid while Stage 67 uses structured grids - the domains are directly coupled by unstructured sliding planes for the unsteady calculation. Each engine has a different axis of rotation and this is included in the domains for each fan.