Aerospace

Conjugate heat and fluid analysis of SDP unit

Objective:

A surveillance data processor (SDP) processes radar and surveillance data. It performs tracking and alert processing for aircraft violating separation minima with other aircraft or restricted airspace. The SDP typically has many heavily componentized cassettes in series and in close proximity to each other. When in operation the device generates copious amounts of heat, therefore making it essential that the instrument cool itself satisfactorily to avoid burnout. A fluid-heat analysis was to be conducted to make the instrument airworthy.

Methodology:

A conjugate heat and fluid analysis was to be conducted on the SDP unit to check the airflow pattern and temperature distribution within the unit. It was modeled with 3D hexahedral elements by an iterative process for several modifications in the flow domain to optimize the flow pattern and temperature distribution. Flow of air was considered incompressible and steady. The instrument was declared airworthy.

Structural analysis of planar printed array antenna

Objective:

Printed array antennas are one of the most sensitive devices on an aircraft, having sensitive electronics on their surfaces that process the data they receive. An antenna needs to be designed optimally and perform satisfactorily in adverse conditions.

Methodology:

The antenna structure was idealized using shell, beam and mass elements. Static analysis was carried out for a range of operating ambient temperature. Dynamic analysis was carried out for shock, sinusoidal and random vibration for the flight envelope.

It was determined that the fundamental frequency was greater than the upper limit specified for frequency sweep. The maximum deflection occurred in crash hazard loading conditions, and the maximum von Mises stress occurred during temperature loading and was a highly localized phenomenon restricted to the fixity region. The antenna was redesigned and passed as airworthy.

Conjugate analysis of C and X band array assembly of ground radar

Objective:

Phased array antennas that can be steered electronically are finding increasing applications in both radar and communication systems. Phased array radar systems offer many advantages over mechanically swept antennas, the most notable being their ability to select a given azimuth and elevation pointing angle without physically moving the antenna. This is probably the best way to track or search many targets widely separated in space. The phase control module (PCM) forms the core element of the phased array radar and helps it in electronic scanning of an RF beam.

PCMs generate heat and many of them in close proximity can increase the surface temperature of the radar surface. Conjugate fluid-heat analyses needed to be carried out on C- and X-band array assemblies to check the flow pattern and temperature distribution within the array housing.

Methodology:

The assemblies were modeled with 3D hexahedral elements and modified iteratively to optimize the air flow pattern and temperature distribution between the PCMs and radar surface. Natural airflow and force airflow from a fan were studied.

The defense department saved on time and expenses by analyzing the simulation rather than physical testing.

Lift and drag analysis of aircraft antenna housing

Objective:

Radar attached to the top of the fuselage of a surveillance plane was to be analyzed for lift and drag force due to the slide of aircraft in the air, at different altitudes, speeds and slide angles.

Methodology:

3D external compressible fluid flow analysis was carried out. The analysis was carried out at different mach numbers, different altitudes and different slide angles. The analysis was carried out at a height of 50,000 feet, Mach number of 0.7 and slide angles of 0°, 5°, and 10° and 20 °. Increase in the slide angle increases the force. The drag forces obtained by parametric study were presented in the table.

Frequency-based composite design for multi-axis gimbal systems

Objective

A company in the USA has developed a line of lightweight, advanced composite, multi-axis gimbals for use in precision applications. A gimbal is a device using Euler angles to measure the rotation of an object in three dimensions and to control that rotation.

To ensure that the structural frequency of the high-modulus gimbal meets the control system specifications, finite element analysis is required to accurately predict its structural response.

Methodology

FEA models are first generated to include composite shell elements, solid bricks for the drive components, and general springs for bearings and fasteners. Spring constants are calculated to represent bearing axial and radial stiffness values, and the fasteners used within the structure. Mass elements are added as required to represent the payload, motor and other ancillary equipment embedded within the gimbal.

Eigenvalue analysis is conducted to extract eigenvalues using the Lanczos method, with stress, strain and displacements saved for post-processing. Composite ply schedules are varied until the first participatory mode meets the control specifications.

The company now has a convenient spreadsheet which has a listing of the modal participation factors of the critical modes. The company saved time and costs by not fabricating a gimbal using a complicated manufacturing process.

Vibration analysis of an aircraft wing and fuselage made of composite material

The use of composites in ultra-light aircrafts is only natural. Low weight and high strength are two attractive features which make them highly desirable. A newly designed all-composite aircraft was to be launched in the market. Stress and vibration analysis was conducted on the wing and fuselage section of the aircraft, after which it was approved for production. The manufacturer saved on time and physical testing costs.

Analysis of an antenna support platform for flightworthiness

The electronics on a satellite antenna are extremely sensitive and delicate. Because of this they need to be supported on a structure which is robust and undergoes minimal deformation during flight. Vibration analysis of an antenna support platform was conducted to qualify the assembly for flightworthiness.

Analysis of satellite for thermal management

A satellite in orbit around the earth is exposed to different temperature conditions at various positions. Any excessive absorption of solar flux by the satellite will result in malfunction of the electronics on board or even compromising of the mission in extreme cases. Thermal analysis was conducted to study the amount of heat absorbed by the faces of the satellite during various orbit positions, to qualify the satellite for safe deployment.

Aircraft tire contact analysis

Aircraft tires are made of multiple plies of composite materials, both metallic and non-metallic, making them extremely difficult to study. An aircraft tire making contact with the tarmac during landing is a high-energy elasto-plastic process extremely detrimental to the tire. Tire contact analysis is paramount to tire companies who would like to increase the durability of their tires. Contact analysis was conducted on the tire under various loadings (aircrafts types, speeds, ground conditions, etc.) to the satisfaction of the manufacturer. The manufacturer saved on exorbitant testing costs associated with these types of physical tests.

Random vibration analysis of antenna cabin

The antenna is an extremely sensitive and delicate part of a satellite. Because of this it is generally placed inside a cabin when being transported and when it is deployed in space. The structural integrity of the cabin is paramount if it has to protect the antenna. Random vibration analysis was conducted on the cabin in the transportation and deployed mode to ensure safe passage of the antenna. The agency saved on time and physical testing costs.

Analysis of an avionic instrument for flightworthiness

Avionics equipment in supersonic combat aircrafts is subject to extreme gravitational forces during certain maneuvers. Any damage to important instrumentation can turn detrimental to the mission. Stress analysis, vibration analysis and modal analysis were conducted to ensure the flightworthiness of an instrument. Various gravitational forces were simulated and design changes to the housing and supports were suggested. The air force saved on time and testing costs.

Analysis of a helium balloon

Hot air balloon enthusiasts need to have an inner helium balloon inside the normal hot air canopy when traveling at high altitudes. The area below the helium balloon forms a cone into which hot air is fired through gas tanks. A hot air balloon enthusiast wished to make a record breaking attempt at flying around the globe non-stop. Computational fluid dynamic analysis was conducted on the balloon which consisted of studying the effect of the sun’s heat on the helium at various times of the day and the optimum amount of heat to be fired into the air cone below the helium balloon to maintain optimum altitude. Highly expensive and cumbersome physical testing was avoided in this case.

Stage separation in space vehicle

Stage separation after lift-off is one of the most crucial maneuvers a space vehicle has to undergo during its mission. Improper separation can cause the space vehicle to go off course and compromise an entire mission. The reactionary force on the two separating surfaces due to a controlled explosion is an important aspect to study. Computational fluid dynamic studies on the two separating surfaces were performed to ensure perfect separation. The agency saved on time and exorbitant testing costs.