Safety & Survivability

Commercial aircraft manufacturers and defense contractors are concerned with safety and survivability issues, which must be addressed in the design stage. Engineering for survivability requires trade-offs between multiple disciplines, such as aerodynamics and stealth; weight and mobility; and comfort and protection.  For example, some aircraft with low radar cross sections (RCSs) have faceted surfaces that affect shape and aerodynamics. HFSS software from ANSYS can address RCS. Engineers can obtain fast and reliable simulations with method of moments and hybrid integral/volume methods together with adaptive mesh refinement.

Modern defense aircraft carry stores internally to reduce RCS. Internal carriage affects shape, structure and aerodynamics. When bay doors open to release stores, they may be buffeted by unsteady flow in and around the cavity. ANSYS CFD software can be applied to improve aerodynamics and reduce the resultant unsteady loads.

Bounded central difference schemes maintain high accuracy without spurious oscillations by introducing enough upwinding to stabilize the numerical method. Out-of-the-box coupling between ANSYS CFD and ANSYS Mechanical packages enables direct calculation of the store’s response to unsteady loads. The Fowcs–Williams Hawkings method enables prediction of far-field noise perceived by distant observers far beyond the extent of the computational domain.

Defense helicopters too must be engineered for survivability. Ideally, these vehicles avoid or delay detection by flying quietly with better rotor technology. ANSYS CFD software, with its dynamic mesh adaptation on structured and unstructured Cartesian meshes, can help to minimize blade–vortex interaction. This optimization can be transferred to the commercial world in minimizing external community noise.

On the battlefield, proper helicopter propulsion system integration can minimize infrared (IR) signature, making it difficult for heat-seeking missiles to lock on. ANSYS CFD software simulates temperature distribution around a vehicle, identifying areas for improvement. These simulations are made faster and easier through the availability of a virtual blade model (based on blade-element theory) to account for time-averaged effects of downwash produced by the helicopter rotor.

Protective armor minimizes damage if the craft is hit. Armor can be designed to withstand ballistic impact with explicit dynamics software. ANSYS CFD technology addresses fire suppressant dispersion systems, which may be activated if armor is penetrated. Crash simulations can be performed with ANSYS LS-DYNA

Gearboxes and other power transmission equipment must remain reliable and durable. ANSYS Mechanical is used to develop prognostic models that monitor the health of the vehicle and improve reliability.

ANSYS software provides the breadth needed to reduce and assess vulnerability to specific threats and hazards as well as the parametric capabilities to optimize tradeoffs. Conducting simulation testing allows engineers to develop a better understanding of how aircraft will function in stressful situations, and limits the need for numerous physical tests. More accurate, less-expensive testing reduces the cost of producing prototypes and the time to market, giving designers the opportunity to create the most effective, state-of-the art aircraft.