Bogdan Marcu | University of Southern California (original) (raw)

Papers by Bogdan Marcu

39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2003

Each single reusable Space Launch Initiative (SLI) booster rocket is an engine operating at a rec... more Each single reusable Space Launch Initiative (SLI) booster rocket is an engine operating at a record vacuum thrust level of over 730,000 lbf using LOX and LH2. This thrust is more than 10 percent greater than that of the Delta IV rocket, resulting in relatively large LOX and LH2 ...

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2006

44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2006

An extensive computational effort has been performed in order to investigate the nature of unstea... more An extensive computational effort has been performed in order to investigate the nature of unsteady flow in the fuel line supplying the three Space Shuttle Main Engines during flight. Evidence of high cycle fatigue (HCF) in the flow liner one diameter upstream of the Low Pressure Fuel ...

38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2002

Boeing-Rocketdyne in collaboration with Mitsubishi Heavy Industries is developing a new upper sta... more Boeing-Rocketdyne in collaboration with Mitsubishi Heavy Industries is developing a new upper stage cryogenic engine, denominated MB60. The engine is destined for the Delta IV vehicle and is rated at 60,000 lbf thrust level. This paper provides a description of the ...

44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008

Pratt and Whitney Rocketdyne and NASA Marshall Space Flight Center are developing the advanced up... more Pratt and Whitney Rocketdyne and NASA Marshall Space Flight Center are developing the advanced upper stage J-2X engine based on the legacy design of the J-2/J-2S family of engines which powered the Apollo missions. The cryogenic propellant turbopumps have been denoted ...

43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005

A threedimensional flow solver has been developed for turbomachinery components utilizing real fl... more A threedimensional flow solver has been developed for turbomachinery components utilizing real fluid properties. The code is applicable to both incompressible and compressible flow fields. In this study, the code has been applied to the analysis of inducer and ~ ___ ____ * Aerospace Engineer, Associate Fellow AIAA.

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2004

Turbomachines for rocket propulsion applications operate with many different working fluids and f... more Turbomachines for rocket propulsion applications operate with many different working fluids and flow conditions. Oxidizer boost turbines often operate in liquid oxygen, resulting in an incompressible flow field. Vortex shedding from airfoils in this flow environment can have adverse effects on both turbine performance and durability. In this study the effects of vortex shedding in a low-pressure oxidizer turbine are investigated. Benchmark results are also presented for vortex shedding behind a circular cylinder. The predicted results are compared with available experimental data.

41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005

The Commoditization of Space Propulsion: Modular Propulsion Based on MEMS Technology. Bogdan Marc... more The Commoditization of Space Propulsion: Modular Propulsion Based on MEMS Technology. Bogdan Marcu, George Prueger, Alan H Epstein, Stuart A Jacobson 41 st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 1-10, 2005. ...

SAE Technical Paper Series, 1998

The contents of this report reflect the views of the authors who are responsible for the facts an... more The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California. This report does not constitute a standard, specification, or regulation.

SAE Technical Paper Series, 1998

The contents of this report reflect the views of the authors who are responsible for the facts an... more The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California. This report does not constitute a standard, specification, or regulation.

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2007

The Space Shuttle Main Engine (SSME) uses a turbine fuel flowmeter (FFM) in its Low Pressure Fuel... more The Space Shuttle Main Engine (SSME) uses a turbine fuel flowmeter (FFM) in its Low Pressure Fuel Duct (LPFD) to measure liquid hydrogen flowrates during engine operation. The flowmeter is required to provide accurate and robust measurements of flow rates ranging from 10000 to 18000 GPM in an environment contaminated by duct vibration and duct internal acoustic disturbances. Errors exceeding 0.5% can have a significant impact on engine operation and mission completion. The accuracy of each sensor is monitored during hot-fire engine tests on the ground. Flow meters which do not meet requirements are not flown. Among other parameters, the device is screened for a specific behavior in which a small shift in the flow rate reading is registered during a period in which the actual fuel flow as measured by afacility meter does not change. Such behavior has been observed over the years for specific builds of the FFM and must be avoided or limited in magnitude in flight. Various analyses of the recorded data have been made prior to this report in an effort to understand the cause of the phenomenon; however, no conclusive cause for the shift in the instrument behavior has been found. The present report proposes an explanation of the phenomenon based on interactions between acoustic pressure disturbances in the duct and the wakes produced by the FFM flow straightener. Physical insight into the effects of acoustic plane wave disturbances was obtained using a simple analytical model. Based on that model, a series of threedimensional unsteady viscous flow computational fluid dynamics (CFD) simulations were performed using the MSFC PHANTOM turbomachinery code. The code was customized to allow the FFM rotor speed to change at every time step according to the instantaneous fluid forces on the rotor, that, in tum, are affected by acoustic plane pressure waves propagating through the device. The results of the simulations show the variation in the rotation rate of the flowmeter due to the interaction of the flow straightener wakes and the upstream propagating acoustic waves. A detailed analysis of the acoustic disturbance effects is presented along with an assessment of the impact on measurement accuracy.

SAE Technical Paper Series, 1999

Axial force, side force and yawing moment are measured on each member of a three-vehicle platoon ... more Axial force, side force and yawing moment are measured on each member of a three-vehicle platoon subject to crosswind conditions. The longitudinal spacing between vehicles is varied from 0 to 0.72 vehicle lengths in a large set of combinations covering both symmetric and ...

Physics of Fluids, 1996

Navier-Stokes simulations of a temporally growing mixing layer are employed to investigate three-... more Navier-Stokes simulations of a temporally growing mixing layer are employed to investigate three-dimensional mechanisms for the dispersion and accumulation of small, heavy, spherical particles. It is found that in particular the presence of the streamwise braid vortices gives rise to additional dynamical effects that modify the concentration, dispersion, and suspension patterns observed in two-dimensional situations. Intense stretching and folding by the evolving three-dimensional vorticity field, when combined with inertial effects such as ejection by the concentrated streamwise vortices, strongly distorts the geometry of both clear fluid and particle laden regions. Different time scales can be associated with the spanwise and streamwise vortices, so that these distinct vortical systems can selectively affect different classes of particles.

Physics of Fluids, 1995

This paper presents a linear stability analysis as well as some numerical results for the motion ... more This paper presents a linear stability analysis as well as some numerical results for the motion of heavy particles in the flow field of a Burgers vortex, under the combined effects of particle inertia, Stokes drag, and gravity. By rendering the particle motion equations dimensionless, the particle Stokes number, a Froude number, and a vortex Reynolds number are obtained as the governing three parameters. In the absence of gravity, the vortex center represents a stable equilibrium point for particles up to a critical value of the Stokes number, as the inward drag overcomes the destabilizing centrifugal force on the particle. Particles exceeding the critical Stokes number value asymptotically approach closed circular orbits. Under the influence of gravity, one or three equilibrium points appear away from the vortex center. Both their locations and their stability characteristics are derived analytically. These stability characteristics can furthermore be related to the nature of the critical points in a related directional force field. These findings are expected to be applicable to the coupling between the small-scale turbulent flow structures and the 'motion of suspended particles. Q 1995 American Institute of Physics.

Physics of Fluids, 1996

The dynamics of small, heavy, spherical particles are investigated in an analytical model of the ... more The dynamics of small, heavy, spherical particles are investigated in an analytical model of the stretched counterrotating streamwise braid vortices commonly found in three-dimensionally evolving mixing layers. The flow field consists of two superimposed rows of Stuart vortices of opposite sign, with an additional two-dimensional strain field. The particle dynamics are determined by a balance of inertial, gravitational, and viscous drag forces, i.e., the dimensionless Stokes and Froude numbers, St and Fr, as well as by the dimensionless strain rate, and the Stuart vortex family parameter. Equilibrium points for the particles, as well as their stability criteria, are determined analytically, both in the absence and in the presence of gravity, and for different orientations of the gravity vector. In the absence of gravity, accumulation of low St particles can occur at the center of the braid vortices. An analytical expression for the critical particle diameter, below which accumulation is possible, is derived. The presence of gravity can lead to the emergence of multiple equilibrium points, whose stability properties depend on their locations. For a horizontal mixing layer flow and strong gravity effects, unconditional accumulation can occur midway between the streamwise braid vortices in the upwelling regions. Conditionally stable accumulation regions exist a short horizontal distance away from the centers of the braid vortices. If the gravity vector lies within the plane of the mixing layer, accumulation points exist only for moderate strengths of gravity. Under these circumstances, conditional accumulation is possible near the streamwise vortex centers.

Measurements of drag, side forces and yawing moment are made for each of a two-vehicle platoon, u... more Measurements of drag, side forces and yawing moment are made for each of a two-vehicle platoon, using 1/8 scale models of 1991 Chevy Lumina minivans equipped with force balances. The models are placed in a wind tunnel in a close following configuration, but with the trailing car placed in reverse - with its back forward towards the leading car - a configuration referred to as a "back-to-back configuration". The vehicle models are supported above a ground plane whose surface is porous. The boundary layer forming on the ground plane is removed by applying a small suction on the porous surface. Measurements are made for longitudinal spacing ranging from 0 to 0.4 vehicle lengths and alignments in the range of 0.025 car widths left to 0.025 car widths right of the centered position Meas urements reveal a very surprising phenomenon: the aerodynamic drag force on the leading vehicle is found to vary from a low value of 0.45 at zero spacing to a peak value of 0.95-1.0 at a spacing...

The dissertation addresses the phenomenon of interaction of small, heavy, spherical particles wit... more The dissertation addresses the phenomenon of interaction of small, heavy, spherical particles with the flow field produced by vortices undergoing extensional strain. By rendering the particle motion equations dimensionless, we obtain as the governing two parameters the particle Stokes and Froude numbers. The first part of the thesis considers the flow around a Burgers vortex. In the absence of gravity, the vortex center represents a stable equilibrium point for particles up to a critical value of the Stokes number. Supercritical St particles asymptotically approach closed circular orbits. Under the influence of gravity, one or three equilibrium points appear away from the vortex center. We derive both their locations and their stability characteristics analytically. In the second part, the particle dynamics is investigated in an analytical model of the stretched counter-rotating streamwise braid vortices commonly found in three-dimensionally evolving mixing layers. Equilibrium point...

39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2003

Each single reusable Space Launch Initiative (SLI) booster rocket is an engine operating at a rec... more Each single reusable Space Launch Initiative (SLI) booster rocket is an engine operating at a record vacuum thrust level of over 730,000 lbf using LOX and LH2. This thrust is more than 10 percent greater than that of the Delta IV rocket, resulting in relatively large LOX and LH2 ...

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2006

44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2006

An extensive computational effort has been performed in order to investigate the nature of unstea... more An extensive computational effort has been performed in order to investigate the nature of unsteady flow in the fuel line supplying the three Space Shuttle Main Engines during flight. Evidence of high cycle fatigue (HCF) in the flow liner one diameter upstream of the Low Pressure Fuel ...

38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2002

Boeing-Rocketdyne in collaboration with Mitsubishi Heavy Industries is developing a new upper sta... more Boeing-Rocketdyne in collaboration with Mitsubishi Heavy Industries is developing a new upper stage cryogenic engine, denominated MB60. The engine is destined for the Delta IV vehicle and is rated at 60,000 lbf thrust level. This paper provides a description of the ...

44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008

Pratt and Whitney Rocketdyne and NASA Marshall Space Flight Center are developing the advanced up... more Pratt and Whitney Rocketdyne and NASA Marshall Space Flight Center are developing the advanced upper stage J-2X engine based on the legacy design of the J-2/J-2S family of engines which powered the Apollo missions. The cryogenic propellant turbopumps have been denoted ...

43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005

A threedimensional flow solver has been developed for turbomachinery components utilizing real fl... more A threedimensional flow solver has been developed for turbomachinery components utilizing real fluid properties. The code is applicable to both incompressible and compressible flow fields. In this study, the code has been applied to the analysis of inducer and ~ ___ ____ * Aerospace Engineer, Associate Fellow AIAA.

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2004

Turbomachines for rocket propulsion applications operate with many different working fluids and f... more Turbomachines for rocket propulsion applications operate with many different working fluids and flow conditions. Oxidizer boost turbines often operate in liquid oxygen, resulting in an incompressible flow field. Vortex shedding from airfoils in this flow environment can have adverse effects on both turbine performance and durability. In this study the effects of vortex shedding in a low-pressure oxidizer turbine are investigated. Benchmark results are also presented for vortex shedding behind a circular cylinder. The predicted results are compared with available experimental data.

41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005

The Commoditization of Space Propulsion: Modular Propulsion Based on MEMS Technology. Bogdan Marc... more The Commoditization of Space Propulsion: Modular Propulsion Based on MEMS Technology. Bogdan Marcu, George Prueger, Alan H Epstein, Stuart A Jacobson 41 st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 1-10, 2005. ...

SAE Technical Paper Series, 1998

The contents of this report reflect the views of the authors who are responsible for the facts an... more The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California. This report does not constitute a standard, specification, or regulation.

SAE Technical Paper Series, 1998

The contents of this report reflect the views of the authors who are responsible for the facts an... more The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California. This report does not constitute a standard, specification, or regulation.

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2007

The Space Shuttle Main Engine (SSME) uses a turbine fuel flowmeter (FFM) in its Low Pressure Fuel... more The Space Shuttle Main Engine (SSME) uses a turbine fuel flowmeter (FFM) in its Low Pressure Fuel Duct (LPFD) to measure liquid hydrogen flowrates during engine operation. The flowmeter is required to provide accurate and robust measurements of flow rates ranging from 10000 to 18000 GPM in an environment contaminated by duct vibration and duct internal acoustic disturbances. Errors exceeding 0.5% can have a significant impact on engine operation and mission completion. The accuracy of each sensor is monitored during hot-fire engine tests on the ground. Flow meters which do not meet requirements are not flown. Among other parameters, the device is screened for a specific behavior in which a small shift in the flow rate reading is registered during a period in which the actual fuel flow as measured by afacility meter does not change. Such behavior has been observed over the years for specific builds of the FFM and must be avoided or limited in magnitude in flight. Various analyses of the recorded data have been made prior to this report in an effort to understand the cause of the phenomenon; however, no conclusive cause for the shift in the instrument behavior has been found. The present report proposes an explanation of the phenomenon based on interactions between acoustic pressure disturbances in the duct and the wakes produced by the FFM flow straightener. Physical insight into the effects of acoustic plane wave disturbances was obtained using a simple analytical model. Based on that model, a series of threedimensional unsteady viscous flow computational fluid dynamics (CFD) simulations were performed using the MSFC PHANTOM turbomachinery code. The code was customized to allow the FFM rotor speed to change at every time step according to the instantaneous fluid forces on the rotor, that, in tum, are affected by acoustic plane pressure waves propagating through the device. The results of the simulations show the variation in the rotation rate of the flowmeter due to the interaction of the flow straightener wakes and the upstream propagating acoustic waves. A detailed analysis of the acoustic disturbance effects is presented along with an assessment of the impact on measurement accuracy.

SAE Technical Paper Series, 1999

Axial force, side force and yawing moment are measured on each member of a three-vehicle platoon ... more Axial force, side force and yawing moment are measured on each member of a three-vehicle platoon subject to crosswind conditions. The longitudinal spacing between vehicles is varied from 0 to 0.72 vehicle lengths in a large set of combinations covering both symmetric and ...

Physics of Fluids, 1996

Navier-Stokes simulations of a temporally growing mixing layer are employed to investigate three-... more Navier-Stokes simulations of a temporally growing mixing layer are employed to investigate three-dimensional mechanisms for the dispersion and accumulation of small, heavy, spherical particles. It is found that in particular the presence of the streamwise braid vortices gives rise to additional dynamical effects that modify the concentration, dispersion, and suspension patterns observed in two-dimensional situations. Intense stretching and folding by the evolving three-dimensional vorticity field, when combined with inertial effects such as ejection by the concentrated streamwise vortices, strongly distorts the geometry of both clear fluid and particle laden regions. Different time scales can be associated with the spanwise and streamwise vortices, so that these distinct vortical systems can selectively affect different classes of particles.

Physics of Fluids, 1995

This paper presents a linear stability analysis as well as some numerical results for the motion ... more This paper presents a linear stability analysis as well as some numerical results for the motion of heavy particles in the flow field of a Burgers vortex, under the combined effects of particle inertia, Stokes drag, and gravity. By rendering the particle motion equations dimensionless, the particle Stokes number, a Froude number, and a vortex Reynolds number are obtained as the governing three parameters. In the absence of gravity, the vortex center represents a stable equilibrium point for particles up to a critical value of the Stokes number, as the inward drag overcomes the destabilizing centrifugal force on the particle. Particles exceeding the critical Stokes number value asymptotically approach closed circular orbits. Under the influence of gravity, one or three equilibrium points appear away from the vortex center. Both their locations and their stability characteristics are derived analytically. These stability characteristics can furthermore be related to the nature of the critical points in a related directional force field. These findings are expected to be applicable to the coupling between the small-scale turbulent flow structures and the 'motion of suspended particles. Q 1995 American Institute of Physics.

Physics of Fluids, 1996

The dynamics of small, heavy, spherical particles are investigated in an analytical model of the ... more The dynamics of small, heavy, spherical particles are investigated in an analytical model of the stretched counterrotating streamwise braid vortices commonly found in three-dimensionally evolving mixing layers. The flow field consists of two superimposed rows of Stuart vortices of opposite sign, with an additional two-dimensional strain field. The particle dynamics are determined by a balance of inertial, gravitational, and viscous drag forces, i.e., the dimensionless Stokes and Froude numbers, St and Fr, as well as by the dimensionless strain rate, and the Stuart vortex family parameter. Equilibrium points for the particles, as well as their stability criteria, are determined analytically, both in the absence and in the presence of gravity, and for different orientations of the gravity vector. In the absence of gravity, accumulation of low St particles can occur at the center of the braid vortices. An analytical expression for the critical particle diameter, below which accumulation is possible, is derived. The presence of gravity can lead to the emergence of multiple equilibrium points, whose stability properties depend on their locations. For a horizontal mixing layer flow and strong gravity effects, unconditional accumulation can occur midway between the streamwise braid vortices in the upwelling regions. Conditionally stable accumulation regions exist a short horizontal distance away from the centers of the braid vortices. If the gravity vector lies within the plane of the mixing layer, accumulation points exist only for moderate strengths of gravity. Under these circumstances, conditional accumulation is possible near the streamwise vortex centers.

Measurements of drag, side forces and yawing moment are made for each of a two-vehicle platoon, u... more Measurements of drag, side forces and yawing moment are made for each of a two-vehicle platoon, using 1/8 scale models of 1991 Chevy Lumina minivans equipped with force balances. The models are placed in a wind tunnel in a close following configuration, but with the trailing car placed in reverse - with its back forward towards the leading car - a configuration referred to as a "back-to-back configuration". The vehicle models are supported above a ground plane whose surface is porous. The boundary layer forming on the ground plane is removed by applying a small suction on the porous surface. Measurements are made for longitudinal spacing ranging from 0 to 0.4 vehicle lengths and alignments in the range of 0.025 car widths left to 0.025 car widths right of the centered position Meas urements reveal a very surprising phenomenon: the aerodynamic drag force on the leading vehicle is found to vary from a low value of 0.45 at zero spacing to a peak value of 0.95-1.0 at a spacing...

The dissertation addresses the phenomenon of interaction of small, heavy, spherical particles wit... more The dissertation addresses the phenomenon of interaction of small, heavy, spherical particles with the flow field produced by vortices undergoing extensional strain. By rendering the particle motion equations dimensionless, we obtain as the governing two parameters the particle Stokes and Froude numbers. The first part of the thesis considers the flow around a Burgers vortex. In the absence of gravity, the vortex center represents a stable equilibrium point for particles up to a critical value of the Stokes number. Supercritical St particles asymptotically approach closed circular orbits. Under the influence of gravity, one or three equilibrium points appear away from the vortex center. We derive both their locations and their stability characteristics analytically. In the second part, the particle dynamics is investigated in an analytical model of the stretched counter-rotating streamwise braid vortices commonly found in three-dimensionally evolving mixing layers. Equilibrium point...