A. Rustem Aslan

Computing Micro Synthetic Jet in Slip Regime With Moving Membrane

A Navier-Stokes (NS) solver for moving and deforming meshes has been modified to investigate numerically the diaphragm-driven flow in and out of two synthetic jet cavity geometries. The piezoelectric-driven diaphragm of the cavity is modeled in a realistic manner as a moving boundary to accurately compute the flow inside the jet cavity. The primary focus of the present paper is to describe the effect of cavity geometry and the wall slip, resulting from the relatively larger Kn number flows associated with micro sized geometries, on the exit jet velocity magnitude. Compressible flow simulations are required for rarefied flows to accurately predict the pressure field. The present computations for the quiescent external flow condition reveal that cavity geometry and the wall slip has an increasing effect on the magnitude of the average jet exit velocity as well as vortex shedding from the orifice.Copyright

Low cost S Band communication system design for nano satellites

Nano satellite structures have limited communication ability due to limited power and size. Most of satellite includes sensors, for instance camera, also image transfer requires more data transfer speed. In this project, 2.4 GHz (S Band) communication system is designed for LEO satellites (700–900 km). System includes system-on-chip transmitter device, preamplifier, band pass filter, power amplifier and microstrip antenna array. Microstrip antenna array and RF circuit is designed on FR4. Microstrip array size is 92×84mm2 and RF circuit size is 38×53mm2. Output power of the system is 35dBm for 2.4kbaud data rate, but it can be increased to power capability of the satellite for more data rate.

Efficient incompressible flow calculations using PQ2Q1 element

Implementation of an equal-order-interpolation velocity–pressure element pair is presented for the finite element solution of incompressible viscous flows. A fractional-step method is employed for temporal discretization. The element pair, also called a pseudo-biquadratic velocity/bilinear pressure element (pQ2Q1), consists of a bilinear pressure element and bilinear velocity elements defined on subdivisions of the pressure element. This pair satisfies the so-called ‘Ladyzhenskaya–Babuska–Brezzi’ condition. Considerable savings in computational cost are achieved due to the reduced number of elements for pressure. A modification of the element is realized for a better representation of curved surfaces. Two test cases, namely the lid-driven cavity flow and impulsively started circular cylinder in cross-flow, are used to assess the accuracy and efficiency of the element compared to a regular bilinear velocity–pressure (Q1Q1) element pair. Computational results presented show that the pQ2Q1 element solutions require less memory and CPU time compared to Q1Q1 element solutions, for at least the same accuracy.

3-D Viscous Flow Solutions Over Bodies in Relative Motion

A space-time finite element method based on the Arbitrary Lagrangian-Eulerian description of the incompressible Navier-Stokes Equations is developed. The developed method is used for predicting the flows past bodies in relative motion. The governing equations are expressed in a fixed frame of reference, wherein the terms related to grid motion are included. Superparametric space-time elements are used in the discretization of the domain in which, finite elements are both allowed to move and deform in (i) simple and (ii) automatic manner. The equations for the rigid body motion are integrated to calculate the trajectory of the moving object under aerodynamic and gravitational forces. The code developed here is first tested on the flow about a drifting and falling sphere which starts to move at Reynolds number of 104 from a steady state. To study the flows about the bodies in relative motion, store-separation from a wing problem is investigated as a turbulent flow for the Reynolds number of 2.5 x 106 based on the length of the store.

3D FLOW CALCULATIONS WITH AN A‐L‐E DESCRIPTION USING SPACE–TIME FINITE ELEMENTS

A space-time finite element method based on an arbitrary Lagrangian-Eulerian description is developed and implemented for the solution of Navier-Stokes equations for predicting the unsteady incompressible flows past arbitrary geometries. The governing equations are expressed in the fixed frame of reference wherein the terms related to grid motion are included. Superparametric space-time elements are used in discretization of the domain in which the finite elements are both allowed to move and deform. The code developed here is calibrated and tested on the flow about a drifting sphere. First, the unidirectionally drifting sphere is set to drift from a steady state at an initial Reynolds number of 1000. In addition, laminar flow about a drifting and falling sphere is studied, starting from the steady state at a Reynolds number of 10,000.

On-board software for HAVELSAT cubesat

HAWELSAT is a 2U CubeSat developed by HAVELSAN and Istanbul Technical University (ITU) as a part of QB50 Project [1] in Turkey. During its mission, HAVELSAT will collect electron density information in its orbit and transfer this data to the ground station (GS). In QB50 program, the aim is to use all collected e-density data from all satellites to get better thermosphere models. In this article, the developed on-board software (SW) and the development phases will be briefly explained. Moreover, a summary of difficulties faced during these phases and also lessons learnt are summarized.

Mission analysis of a 2U CubeSat, BeEagleSat

This paper presents the orbital mission analysis of BeEagleSat, one of the participants of QB50 project, double unit CubeSat of Istanbul Technical University and Turkish Air Force Academy. The BeEagleSat will gather science data in the upper layers of the troposphere in the altitude range between 380 km and 200 km. Starting with the proposed launch parameters and restrictions of the project, simulations have been carried out in order to obtain the lifetime, communication ability and sunlight duration of BeEagleSat. The analysis shows that BeEagleSat is able to satisfy the project requirements.

A refinement of asymptotic predictions and full numerical solution of helicopter rotor noise in the far field

The asymptotic analysis of Parry and Crighton [1] for propeller noise in the far field, which is based on Hansons formulation [2] of the FW-H equation, is refined to second order by Laplaces method [3] for evaluating integrals, accounting for second order contributions near the blade tip for loading and thickness noise. The full numerical solution of Hansons integrals for both thickness and loading noise is also presented. In particular, the theory is applied to a four-bladed helicopter rotor with tip Mach numbers ranging between 0.5 and 0.7. The aerodynamic loading in this case is obtained using a 3D compressible code based on finite volume method with intensified grid density near the blade tip. The far field angular SPL noise distributions of a helicopter rotor in hover show that the present second order asymptotic formula is in better agreement with full numerical computations than that of the first order formula, especially for thickness noise.