Papers by Cedrick Ngalande
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. the flow regimes from near free molecular to near continuum. In the experiment, the vane is resistively heated to about 419 K on one side and 394 K on the other side, and immersed in a rarefied argon gas. The radiometric force is then measured on a nano-Newton thrust stand in a 3 m vacuum chamber and compared with the present numerical predictions and analytical predictions proposed by various authors. The computational modeling is conducted with a kinetic approach based on the solution of ES-BGK equation. Numerical modeling showed the importance of regions with elevated pressure observed near the edges of the vane for the radiometric force production. A simple analytic expression is proposed for the radiometric force as a function of pressure, that is found to be in good agreement with experimental data. The shear force on the lateral side of the vane was found to decrease the total radiometric force. Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified SAR 16 19b. TELEPHONE NUMBER (include area code) N/A Standard Form 298 (Rev. 8-98)
45th AIAA Aerospace Sciences Meeting and Exhibit, 2007
39th AIAA Thermophysics Conference, 2007
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
37th AIAA Plasmadynamics and Lasers Conference, 2006
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2010
... Pumping statistics were built from individual particle dynamics to represent the physical pro... more ... Pumping statistics were built from individual particle dynamics to represent the physical problem. ... Plasma Sci. 23, 581 (1995). T.Gierczak, RKTalukdar, SCHerndon, GLVaghjiani, and ARRavishankara, J. Phys. Chem. A 101, 3125 (1997). JEChirivella, Jet Propul. Lab. Q. Tech. ...
Journal of Spacecraft and Rockets, 2006
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
The objective of this study is the numerical analysis of gas flow rarefaction phenomena with appl... more The objective of this study is the numerical analysis of gas flow rarefaction phenomena with application to a number of aerospace-related problems. The understanding and accurate numerical prediction of rarefied flow regime is important both for aerospace systems that operate in this regime, and for the development of new generation of gasdriven nano- and micro-scale devices, for which the gas mean free path is comparable with the reference flow scale and rarefaction effects are essential. The main tool for the present analysis is the direct simulations Monte Carlo (DSMC) method. The first topic is the study of rarefied flows in the CHAFF-IV facility. A test particle method was used to analyse the pumping efficiency of CHAFF-IV, and determine optimum geometrical configuration of the chamber. The second topic under consideration is the influence of the surface roughness on nozzle plume flow and plume impingement for different flow regimes from free molecular to near-continuum. Surface roughness effects in rocket nozzles are found to be significant only in very rarefied flows where Reynolds number is about unity. The third topic is the effect of rarefaction on radiometric forces. This effect is shown to be an important factor affecting the radiometric forces. The maximum radiometric forces for all gases under consideration are observed at a Knudsen number of about 0.1. For a radiometer vane placed in a finite size chamber, the maximum force was found to be roughly proportional to the surface area of the vane. This is an indication that the collision-less area force, and not thermal transpiration edge force, dominates the radiometric phenomena in that regime. The role of molecular diameter, viscosity and chamber size on radiometric forces have been found to be significant. The forth topic is the numerical study of the interaction between optical lattices created by two counter-propagating laser beams and initially stagnant gases, in the entire flow regime from free molecular to continuum. It has been shown that in a weekly collisional regime optical lattices can trap and accelerate neutral molecules from room temperature level to tens of kilometers over a single laser pulse. In the collisional regime, the optical lattice---gas interaction was found to result in strong energy and momentum deposition to the gas. Two types of optical lattice-based micropropulsion devices have been proposed for low and high density regimes. For the high density microthruster, an optical lattice is used to deposit energy and momentum to the region near the nozzle throat with subsequent increase in propulsion efficiency. In the low density microthruster, a multiple orifice flow is considered, and thrust is produced by molecules accelerated to high velocities by a chirped lattice potential.
Physical Review E, 2009
The radiometric force on several configurations of heated plates placed in a stagnant gas is exam... more The radiometric force on several configurations of heated plates placed in a stagnant gas is examined experimentally, with a high-resolution thrust stand, and numerically using the direct simulation Monte Carlo method and a discrete ordinate solution of a model kinetic equation. A wide range of pressures from 0.006 to 6 Pa was examined, corresponding to Knudsen numbers from 20 to 0.02, in argon and helium test gases. The radiometric force, important in a number of emerging micro- and nanoscale applications, is shown to be mostly area dependent in the transitional regime where it reaches its maximum at Kn approximately 0.1.
Radiometric Force Actuation (RFA) refers to a non-equilibrium phenomenon when a total force is ex... more Radiometric Force Actuation (RFA) refers to a non-equilibrium phenomenon when a total force is exerted on an object submerged into a gas under the conditions of temperature inequality between the object and the gas container walls. The thermal stresses in the gas generate a flow which results in a force which has a maximum in rarefied regime. The flow is called ``radiometric'' because it is similar to the gas flow that rotates the vanes of Crookes' radiometer. This gas flow phenomenon combined with modern low heat-conductivity materials can be exploited to create microactuators driven by radiant or resistive heating. Two kinetic methods - the direct simulation Monte Carlo, a stochastic approach, and the discrete-ordinate solution of ES/BGK equation, a deterministic approach, are applied for analysis of the radiometric flow generated by an non-uniformly heated plate. The dependence of the radiometric force on the Knudsen number is examined as well as the effects of the non-uniform temperature distribution across the plate.
Physics of Fluids, 2007
A two-step kinetic/continuum approach has been used to study the ability of optical lattices to i... more A two-step kinetic/continuum approach has been used to study the ability of optical lattices to improve mixing rates of neutral gas mixtures. The kinetic step uses the direct simulation Monte Carlo method to model the gas-lattice interaction over the laser pulse period. The continuum step based on the solution of Navier-Stokes equations utilizes the kinetic solution as initial condition, and predicts the gas evolution at spatial and temporal scales larger than those associated with the optical lattice.
Journal of Propulsion and Power, 2007
Journal of Fluid Mechanics, 2009
... NATHANIEL SELDEN1, CEDRICK NGALANDE1, NATALIA GIMELSHEIN2, SERGEY GIMELSHEIN2† AND ANDREW KET... more ... NATHANIEL SELDEN1, CEDRICK NGALANDE1, NATALIA GIMELSHEIN2, SERGEY GIMELSHEIN2† AND ANDREW KETSDEVER3 1University of Southern California, Los Angeles ... Even today, the issues does not seem to be fully settled (Scandurra, Iacopetti & Colona 2007). ...
The direct simulation Monte Carlo method is used to study the feasibility of new propulsion conce... more The direct simulation Monte Carlo method is used to study the feasibility of new propulsion concepts based on the interaction of an optical lattice with gas molecules. Two regimes are considered, high density and low density. In the first one, a de Laval nozzle is examined with the carrier gas driven by energy and momentum deposition from the lattice to the region near the nozzle throat. Analytical expressions are developed and compared with the numerical predictions, that describe the energy and momentum energy transfer between the lattice and the gas. In the second regime, a multiple orifice flow is considered with molecules accelerated to high velocities by a chirped lattice potential. Specific impulse of about 500 is obtained with the total thrust of over 10 µN per single 100 µm orifice.
A two-step kinetic/continuum approach has been used to study the ability of optical lattices to i... more A two-step kinetic/continuum approach has been used to study the ability of optical lattices to improve mixing rates of neutral gas mixtures. The kinetic step uses the direct simulation Monte Carlo method to model the gas-lattice interaction over the laser pulse period. The continuum step based on the solution of Navier-Stokes equations utilizes the kinetic solution as initial condition, and predicts the gas evolution at spatial and temporal scales larger than those associated with the optical lattice.
Nonresonant interaction of an optical lattice created by two counterpropagating laser fields with... more Nonresonant interaction of an optical lattice created by two counterpropagating laser fields with gas molecules is studied with the direct simulation Monte Carlo method. Energy and momentum deposition from lattice to gas in the collision regime are examined and the ability of a lattice to increase gas temperature to thousands of kelvins in a single pulse is shown.
Applied Physics Letters, 2007
Nonresonant interaction of an optical lattice created by two counterpropagating laser fields with... more Nonresonant interaction of an optical lattice created by two counterpropagating laser fields with gas molecules is studied with the direct simulation Monte Carlo method. Energy and momentum deposition from lattice to gas in the collision regime are examined and the ability of a lattice to increase gas temperature to thousands of kelvins in a single pulse is shown.
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Papers by Cedrick Ngalande