Effective of Passive Devices in Alleviation of Flow-induced oscillations of he nozzles of a Multi-Booster Launch vehicle

Wind tunnel tests to quantify the flow induced oscillations of nozzles of strap-on boosters of a typical launch vehicle have been performed under jet-off conditions in the Mach number range 0.8 to 2.5. The effects of gymballing the nozzles on the steady and unsteady radial and tangential moments acting at the simulated position of gymbal actuators have been studied. The loads are seen to increase as the gymbal angle increases. The effectiveness of various load alleviating passive devices in reducing steady and unsteady loads was evaluated. The most effective device was found to be a semi-circular segment. The spectra of unsteady moments indicate that the loads alleviating devices do not significantly alter the magnitude as compared to that of the baseline data

Measurement Of Pitch-Damping Derivatives On Prithvi Model In The Nal 1.2m Tunnel

Pitch Damping Derivatives Were Measured On A 1/12 .5 Scale Prithvi Model Using The Forced Oscillation Technique In The NAL 1 .2m Tunnel. The Tests Were Made In The Mach Number Range Of 1 .5 To 3 .0 And At Angles Of Attack 0, 3 And 6 Deg . The Tests Were Conducted For Two Axes Of Oscillation Located At 3 .8 And 4 .05 Times The Body Diameter From The Nose. While A Majority Of The Tests Were Conducted On The 'Plus' Configuration, A Few Tests Were Also Conducted On The Into Configuration To Study The Effect Of Roll Orientation Of The Model . Both Configurations Exhibited Positive Damping Over The Range Of Test Parameters. Effects Of Angle Of Attack And Model Roll Orientation Were Found To Be Small

Interaction of NH3_3 gas on α\alpha-MoO3_3 nanostructures −- a DFT investigation

The structural stability, electronic properties and NH$_3$ adsorption properties of pristine, Ti, Zr and F substituted $\alpha$-MoO$_3$ nanostructures are successfully studied using density functional theory with B3LYP/LanL2DZ basis set. The structural stability of $\alpha$-MoO$_3$ nanostructures is discussed in terms of formation energy. The electronic properties of pristine, Ti, Zr and F incorporated $\alpha$-MoO$_3$ nanostructures are discussed in terms of HOMO-LUMO gap, ionization potential and electron affinity. $\alpha$-MoO$_3$ nanostructures can be fine-tuned with suitable substitution impurity to improve the adsorption characteristics of ammonia, which can be used to detect NH$_3$ in a mixed environment. The present work gives an insight into tailoring $\alpha$-MoO$_3$ nanostructures for NH$_3$ detection.Comment: 16 pages, 20 figures, 2 table

Estimation of stability derivatives and dynamic stability characteristics of basic and AEW HS-748 aircraft

Longitudinal and lateral stability derivatives of the basic and the AEW configurations of the HS-748 aircraft have been estimated. DATCOM and ESDU Data Sheet methods were employed to estimate the complete set of derivatives of the basic aircraft. Derivatives of the AEW aircraft were obtained by a judicious use of some of the measured static wind-tunnel force and moment data in the estimation scheme. Stick-fixed and stick-free dynamic stability characteristics of the basic and the AEW aircraft were computed using the estimated stability derivatives for a range of values of the aircraft weight and C.G. location. The dynamic stability characteristics are expressed in terms of the period, damping and time-to-half amplitude of the different modes of longitudinal and lateral motions. Both the basic and the AEW aircraft are found to be stable in all modes except the spiral mode, which exhibits a mild divergence. Damping of the lateral oscillatory mode with rudder-free, although positive, is rather low for both the basic and the AEW configurations. In general, installation of rotodome reduces the effectiveness of horizontal and vertical stabilizers and also the control effectiveness of the elevator and rudder, but it does not cause any major qualitative changes In the dynamic stability characteristics of the aircraft

Sensing behavior of acetone vapors on TiO2_2 nanostructures --- application of density functional theory

The electronic properties of TiO$_2$ nanostructure are explored using density functional theory. The adsorption properties of acetone on TiO$_2$ nanostructure are studied in terms of adsorption energy, average energy gap variation and Mulliken charge transfer. The density of states spectrum and the band structure clearly reveals the adsorption of acetone on TiO$_2$ nanostructures. The variation in the energy gap and changes in the density of charge are observed upon adsorption of acetone on n-type TiO$_2$ base material. The results of DOS spectrum reveal that the transfer of electrons takes place between acetone vapor and TiO$_2$ base material. The findings show that the adsorption property of acetone is more favorable on TiO$_2$ nanostructure. Suitable adsorption sites of acetone on TiO$_2$ nanostructure are identified at atomistic level. From the results, it is confirmed that TiO$_2$ nanostructure can be efficiently utilized as a sensing element for the detection of acetone vapor in a mixed environment.Comment: 13 pages, 14 figures, 3 table

New approach for modelling strain induced precipitation of Nb(C,N) in HSLA steels during multipass hot deformation in austenite

A new model for strain induced precipitation of Nb(C,N) is developed from the existing model for single pass hot deformation. This new model can be extended to multipass deformation to explain the microstructural evolution during the hot deformation of Nb supersaturated high strength low alloy (HSLA) steels. The key feature of this model is the microband geometry employed, which leads to determination of the local solute concentration at microbands, and hence the potential for carbonitride precipitation on the microbands. The model also validates the need for concurrent growth and coarsening processes, even at the early stages of precipitation. The evolution of the precipitate radius, number density and volume fraction are compared with the experimental results obtained from thin foil TEM micrographs on Fe-30 wt-%Ni alloys ( that are austenitic at room temperature and are similar to HSLA steels in deformation behaviour) subjected to deformation by plane strain compression. The model predictions are in good agreement with experimental results

The Process of Generating Single Large Combined Cloud for Grid-Free Solvers

Dealing with moving body problems, where one component moves relatively with respect to other, is a difficult task in CFD due to the efforts needed in grid handling for every delta change in position of the moving component. The inherent nature of mesh-free solvers reduces the efforts needed for these kinds of problems by operating on a cloud of points rather than a grid. A new method to handle moving body problems is proposed, where individual clouds are generated around each component and are combined into a single large combined cloud. The proposed method is applied to store separation problem and results generated using NAL-MCIR mesh-less solver is compared with experimental results

Nitrogen dioxide and ammonia gas molecules interaction studies on phosphorene nanosheet --- a DFT investigation

The adsorption behaviour of hazardous gas molecules, namely nitrogen dioxide (NO$_2$) and ammonia (NH$_3$), on phosphorene nanosheet (PNS) was explored by means of ab initio technique. To improve the structural solidity of pristine PNS, we have introduced the passivation of hydrogen and fluorine at the terminated edge. The structural solidity of both hydrogen and fluorine passivated PNS is verified in terms of formation energy. The main objective of this research work is to probe NO$_2$ and NH$_3$ gases using PNS as a base sensing material. The adsorption of various preferential adsorption sites of these gas molecules is studied in accordance with the average HOMO-LUMO gap changes, natural-bond-orbital (NBO) charge transfer, HOMO-LUMO gap, and adsorption energy. Notably, the negative value of adsorption energy is found upon the adsorption of NO$_2$ and NH$_3$ on PNS and it is in the range of $-1.36$ to $-2.45$ eV. The findings of the present research work recommend that the hydrogenated and fluorinated PNS can be effectively used as a chemical sensor against NO$_2$ and NH$_3$ molecules.Comment: 15 pages, 21 figures, 2 table