Structural Dynamics and Acoustics

GCAS's experience spans many years of aerospace product development in structural dynamics and acoustic analysis, testing, and noise control. Specific project experience includes:

  • Prediction of the interior noise of aircraft due to wing-mounted propeller excitation
  • Jet exhaust noise prediction using numerical methods from turbulence models as well as semi-empirical methods based on test data
  • Jet exhaust noise measurements, including noise source surveys of plumes and correlation with turbulence measurements
  • Jet exhaust nozzle and suppressor design from predictions and substantiation of levels from measurements
  • Propeller, fan, compressor, and turbine noise predictions from the unsteady aerodynamic field established on the airfoil by upstream wakes, turbulent inflow, or the shock field generated at supersonic speeds
  • Acoustic testing of fans, propellers, compressors, and turbines for sound level correlation with the unsteady flow field
  • Semi-empirical prediction models of combustion noise from experiments
  • The sound field generated within the combustor during liquid rocket combustion instability
  • Noise path discrimination and identification
  • Noise generated in turbulent boundary layers and wakes, including the effect of surface roughness on self-noise
  • Structural-borne noise, such as from vibration generated by engines, pumps, and equipment through the structure to cavities and panels
  • Prediction of low-level noise from motors, pumps, electrical equipment, and hydraulic systems
  • Impact noise prediction and measurement
  • Acoustic treatment design and testing
  • Flow noise in pipes and ducts
  • Prediction methods for the flow-induced noise over submarines
  • Effectiveness of submarine hull coating on echo reduction
  • Acoustic fluid-structure interaction for predicting the interior noise in aircraft fuselages, automobile interiors, and submarine hulls
  • Noise radiation pattern prediction and measurement from structural surfaces
  • Acoustic reverberation room and an echoic chamber design and check out
  • Accuracy and precision of acoustic measurements
  • Reverberation room measurements of satellite panels, electronic packages, and other sensitive equipment
  • Correlation of reverberation room environment to actual flight environment
  • General noise surveys of communities, factories, airports, etc., to meet FAA, OSHA, and other governmental noise regulations
  • Design of control rooms, computer rooms, work areas, etc., for low-noise
  • Correlation and coherence analysis of acoustic and other time series analysis
  • Acoustic fatigue analysis of structures, including the effect of the dynamics of the structure, such as with panels
  • Sound propagation effects, including air attenuation and density gradients
  • Effect of surface reflections on measured sound levels
  • Sound enclosure design
  • Design of specialized noise measurement equipment, such as probe stems, directional arrays, and mirrors

The following describes some of the contracts we have had in Structural Dynamics and Acoustics:

In the area of dynamic testing, GCAS has three retail test systems products:

SDA PROJECTS

The following describes some of the contracts we have had in Structural Dynamics and Acoustics:

  • Blast and Shock Analysis for Vulnerability Codes: In this contract, we are developing new techniques for characterizing Blast waves and shocks striking a vehicle
  • Pressure Vibration Temperature Controller (PVTC): In this contract, we developed the control system for introducing shock, acoustic blast waves, and vibration to the missile structure as well as "steady-state" airflow, pressure, and temperature levels for the US Navy Pacific Missile Testing facility
  • Vulnerability Code Software Development: In this contract for Wright Patterson Air Force Base, we wrote a graphical editor and data translator to and from the Fastgen Vulnerability code and the NASTRAN structural dynamics code
  • VC100: The VC100 is a commercial product described as a real-time PC-based analyzer and signal generator. In addition to continuous vibration signal output, shock output can be generated with various shapes, and the resulting acceleration measurements are analyzed using the Shock Response Spectra technique
  • Wake/Structure Interaction Interior Noise: In this NASA Lewis contract, we developed software to predict unsteady aerodynamics, sound propagation, and interior fuselage noise from the interaction of next-generation prop fan wakes with the downstream wing and fuselage structure

In the area of dynamic testing, GCAS has three retail test systems products:

  • CCAS: In a joint effort with one of the world's leading accelerometer manufacturers, ENDEVCO, GCAS has developed software for controlling up to 1080 amplifiers simultaneously for use in large, complex mechanical tests. This system controls the banks of amplifiers through an IEEE 488 bus. In addition to maintaining the set-up information on the amplifier gains, phase, and other relevant data, CCAS provides real-time monitoring of the RMS signal level on each channel during testing.
  • VC100: The VC100 is a full-function real-time analyzer and signal generator. Transient or continuous waveforms can be generated of any spectral shape and output as an excitation function. Transient or continuous data can be captured and analyzed in either the frequency or time domain using a high-speed array processor. A 1024 point FFTs can be calculated in 18 milliseconds. Transfer functions are calculated using cross-spectral analysis methods to determine the Transfer Function, Frequency Response Function, and Coherence of two simultaneous signal measurements. Signal Source information is then obtained from such cross-spectral calculations by evaluating the phase correlations of the signals.
  • PVTC: The Programmable Vibration and Temperature Controller (PVTC) is a multipurpose, Thermo/Dynamic Control System for reliability testing. The system can simultaneously control up to ten (10) independent Vibration /Acoustic loops. Up to three (3) channels can be averaged for control in either an open or closed loop. The output is a continuous Gaussian random signal mixed with any user-selected pre-stored shock waveform of up to 1.6 seconds in duration. Temperature is controlled using two full PID loops for heating and cooling over the range from -132 to 752 degrees Fahrenheit. Nineteen (19) TTL outputs and eight (8) TTL inputs are also monitored and controlled.