David Tamburello

Three-dimensional interactions of a free jet with a perpendicular synthetic jet

Three-dimensional interaction of an axisymmetric free jet with a single synthetic jet that is oriented perpendicular to the free jet was investigated experimentally using PIV. The main objective was to investigate the effect of the upstream location of the synthetic jet, inside the nozzle of the main jet ( Re U e = 6600). The interaction location of the synthetic jet (for a range of momentum coefficients) was varied from 0.4 to 1.4 orifice diameters upstream of the main jet exit plane. The synthetic jet was driven at a frequency of 1000 Hz, which corresponds to a Strouhal number of 0.16 (within the range of unstable modes of the free jet). To better explore the complex flow field resulting from the interaction, a reduction technique was used where 3D flow renderings were calculated from multiple 2D measurement planes. The interaction is affected by two mechanisms: (1) direct impact of the synthetic jet into the main jet, and (2) amplification of unstable modes of the main jet. When the momentum coefficien...

Manipulation of an axisymmetric jet using continuous control jets

The mechanisms associated with the interaction of an axisymmetric free jet (d e = 4 mm; Re U e = 26 500 and 6600) with two continuous control jets on mixing, spreading and direction were examined experimentally. The flow field was visualized and measured using particle image velocimetry, where the interaction of the main jet with the control jets was investigated for different momentum coefficients, streamwise interaction locations and Reynolds numbers. Applying control at low momentum coefficients results in a stabilizing effect, where near the orifice the main jet is stretched such that the turbulent quantities are decreased. However, when control is applied at high momentum coefficients, enhanced mixing and destabilization is obtained, as well as an earlier transition to turbulence and an alteration of the large coherent structures of the main jet. Moreover, the effectiveness of the control jets in altering the main jet flow is more pronounced when the interaction occurs closer to the main jet exit as well as at lower Reynolds numbers.

Interaction of a free jet with a perpendicular control jet

The effects of the upstream location of a single continuous control jet (i.e., within the main jet nozzle) on an axisymmetric free jet, at Reynolds numbers of 6600 and 26 500, were investigated experimentally using PIV. The control jet was oriented perpendicular to the main jet flow and its momentum coefficient was varied for each Reynolds number. The resultant mean flow field and the turbulent stresses were examined in two planes, along and across the control jets line of action. When the control jet is located near the main jet exit plane, the main jet is vectored away from the control jet due to the direct impact of the control jet. Conversely, with the control jet located farther upstream (i.e., into the nozzle), the main jet is drawn back toward the control jet, which may be as a result of a virtual modification of the nozzle shape. Furthermore, the direction of the main jet can also be controlled by varying the momentum coefficient of the control jet at a fixed upstream location. Finally, the effec...

ENVIRONMENTAL REACTIVITY OF SOLID STATE HYDRIDE MATERIALS: MODELING AND TESTING FOR AIR AND WATER EXPOSURE

To make commercially acceptable condensed phase hydrogen storage systems, it is important to understand quantitatively the risks involved in using these materials. A rigorous set of environmental reactivity tests have been developed based on modified testing procedures codified by the United Nations for the transportation of dangerous goods. Potential hydrogen storage material, 2LiBH4{center_dot}MgH2 and NH3BH3, have been tested using these modified procedures to evaluate the relative risks of these materials coming in contact with the environment in hypothetical accident scenarios. It is apparent that an ignition event will only occur if both a flammable concentration of hydrogen and sufficient thermal energy were available to ignite the hydrogen gas mixture. In order to predict hydride behavior for hypothesized accident scenarios, an idealized finite element model was developed for dispersed hydride from a breached system. Empirical thermodynamic calculations based on precise calorimetric experiments were performed in order to quantify the energy and hydrogen release rates and to quantify the reaction products resulting from water and air exposure. Both thermal and compositional predictions were made with identification of potential ignition event scenarios.

Dynamic response of a free jet following the activation of a single synthetic jet

The transitory behavior of an axisymmetric free jet (Re U e = 6600) with a single synthetic jet, inclined at a 30° angle with respect to the main jet centerline, was investigated experimentally using PIV. The dynamic response of the main jet was measured immediately following the activation of the synthetic jet. The synthetic jet was driven at a frequency of 1000 Hz, which corresponds to a Strouhal number of 0.16 (within the range of unstable modes of the free jet). Three-dimensional flow renderings were calculated from multiple two-dimensional measurement planes to explore the complex three-dimensional flow field resulting from the interaction. Using this technique, it was shown that the transitory response is highly three-dimensional and occurs within the first four synthetic jet actuation cycles. Moreover, the synthetic jets effect on the main jet flow field is felt throughout the measurement domain after only two synthetic jet cycles. Measurements of the streamwise vorticity showed that the interacti...