This page has only limited features, please log in for full access.
To better understand the wake effects at low Reynolds numbers, large-eddy simulations of a 50% reaction low-pressure turbine stage and a linear cascade with two different bar wake generators were carried out for a chord Reynolds number of 50,000. For the chosen front-loaded high-lift airfoil, the endwall structures are stronger than for more traditional mid-loaded moderate-lift airfoils. By comparing the 50% reaction stage results with the bar wake generator results, insight is gained into the effect of the three-dimensional wake components on the downstream flow field.For the cases with bar wake generator, the endwall boundary layer is growing faster because of the relative motion of the endwall with respect to the freestream. The half-width of the wake is approximately matched for the larger one of the two considered bar wake generators. To improve the quality of the phase-averaged flow fields, the proper orthogonal decomposition was employed as a filter to remove the low-energy unsteady flow field content. Both the mean flow and filtered phase-averaged flow fields were analyzed in detail. Visualizations of the phase-averaged flow field reveal a periodic suppression of the laminar suction side separation from the downstream airfoil even for the smaller bar wake generator. The passage vortex is entirely suppressed for the 50% reaction stage and for the larger bar wake generator. Furthermore, the phase-averaged data for the 50% reaction stage reveal a new longitudinal flow structure that is traced back to near-wall wake vorticity. This flow structure is missing for the bar wake generator cases.
Zachary Robison; Andreas Gross. Large-Eddy Simulation of Low-Pressure Turbine Cascade with Unsteady Wakes. Aerospace 2021, 8, 184 .
AMA StyleZachary Robison, Andreas Gross. Large-Eddy Simulation of Low-Pressure Turbine Cascade with Unsteady Wakes. Aerospace. 2021; 8 (7):184.
Chicago/Turabian StyleZachary Robison; Andreas Gross. 2021. "Large-Eddy Simulation of Low-Pressure Turbine Cascade with Unsteady Wakes." Aerospace 8, no. 7: 184.
A technology gap persists in the visualization of optically inaccessible flow fields such as those in integrated systems. Advances in positron emission tomography (PET) technology are enabling its use in the engineering field to address this technology gap. This paper discusses a numerical study performed to characterize a modern PET system’s ability to reconstruct a three-dimensional mapping of the optically inaccessible flow field downstream of an orifice. A method was devised to simulate a ring detector response to a flourine-18 radioisotope/water solution injected into the flow through a standard thickness pipe with orifice. A commercial computational fluid dynamics code and the GEANT4 Applications for the Tomographic Emission Monte Carlo simulation physics package were used to carry out the simulations. Results indicate that geometrical features, such as the pipe internal diameter, can be resolved to within a few millimeters with specific activity levels of 155 Bq/Voxel (91.2 Bq/mm3), and acquisition times as low as 15 s. Results also suggest that flow features, such as the radial extent of the shear layer between the primary and secondary recirculating flow can be resolved to within 5 mm with the same activity level, but with acquisition times of 45 s.
Jeremy Bruggemann; Andreas Gross; Stephen Pate. Non-Intrusive Visualization of Optically Inaccessible Flow Fields Utilizing Positron Emission Tomography. Aerospace 2020, 7, 52 .
AMA StyleJeremy Bruggemann, Andreas Gross, Stephen Pate. Non-Intrusive Visualization of Optically Inaccessible Flow Fields Utilizing Positron Emission Tomography. Aerospace. 2020; 7 (5):52.
Chicago/Turabian StyleJeremy Bruggemann; Andreas Gross; Stephen Pate. 2020. "Non-Intrusive Visualization of Optically Inaccessible Flow Fields Utilizing Positron Emission Tomography." Aerospace 7, no. 5: 52.
Ion-selective membranes are an important component of electrodialysis stacks for desalination. Manufacturing imperfections or slight inhomogeneity of the material can lead to minute membrane surface imperfections. Two-dimensional solutions of the coupled Poisson–Nernst–Planck and Navier–Stokes equations were sought for a perfectly smooth membrane and for membranes with well-defined small-amplitude harmonic surface roughness. The simulations were carried out with the validated rheoEFoam solver by Pimenta and Alves. In the overlimiting regime, the electric field is strong enough for an electrokinetic instability to occur. The instability leads to disturbance growth and the formation of electro-convection cells, which strongly increase the current density. The present simulations show that with an increasing ion concentration and applied voltage, the instability becomes stronger and the overlimiting regime is reached earlier. The limiting current density shows a noticeable dependence on the wavelength of the surface roughness. When the wavelength of the surface roughness is incommensurate with the wavelength of the naturally occurring instability, the limiting current density is increased. Since production membranes will always have some degree of surface roughness, this suggests that membrane surface treatments which favor certain wavelengths may have an effect on the overall membrane performance.
Andreas Gross; Arthur Morvezen; Pedro Castillo Gomez; Xuesong Xu; Pei Xu. Numerical Investigation of the Effect of Two-Dimensional Surface Waviness on the Current Density of Ion-Selective Membranes for Electrodialysis. Water 2019, 11, 1397 .
AMA StyleAndreas Gross, Arthur Morvezen, Pedro Castillo Gomez, Xuesong Xu, Pei Xu. Numerical Investigation of the Effect of Two-Dimensional Surface Waviness on the Current Density of Ion-Selective Membranes for Electrodialysis. Water. 2019; 11 (7):1397.
Chicago/Turabian StyleAndreas Gross; Arthur Morvezen; Pedro Castillo Gomez; Xuesong Xu; Pei Xu. 2019. "Numerical Investigation of the Effect of Two-Dimensional Surface Waviness on the Current Density of Ion-Selective Membranes for Electrodialysis." Water 11, no. 7: 1397.
When a laminar boundary layer is subjected to an adverse pressure gradient, laminar separation bubbles can occur. At low Reynolds numbers, the bubble size can be substantial, and the aerodynamic performance can be reduced considerably. At higher Reynolds numbers, the bubble bursting can determine the stall characteristics. For either setting, an active control that suppresses or delays laminar separation is desirable. A combined numerical and experimental approach was taken for investigating active flow control and its interplay with separation and transition for laminar separation bubbles for chord-based Reynolds numbers of Re ≈ 64,200–320,000. Experiments were carried out both in the wind tunnel and in free flight using an instrumented 1:5 scale model of the Aeromot 200S, which has a modified NACA 643-618 airfoil. The same airfoil was also used in the simulations and wind tunnel experiments. For a wide angle of attack range below stall, the flow separates laminar from the suction surface. Separation control via a dielectric barrier discharge plasma actuator and unsteady blowing through holes were investigated. For a properly chosen actuation amplitude and frequency, the Kelvin–Helmholtz instability results in strong disturbance amplification and a “roll-up” of the separated shear layer. As a result, an efficient and effective laminar separation control is realized.
Andreas Gross; Hermann F. Fasel. Active Control of Laminar Separation: Simulations, Wind Tunnel, and Free-Flight Experiments. Aerospace 2018, 5, 114 .
AMA StyleAndreas Gross, Hermann F. Fasel. Active Control of Laminar Separation: Simulations, Wind Tunnel, and Free-Flight Experiments. Aerospace. 2018; 5 (4):114.
Chicago/Turabian StyleAndreas Gross; Hermann F. Fasel. 2018. "Active Control of Laminar Separation: Simulations, Wind Tunnel, and Free-Flight Experiments." Aerospace 5, no. 4: 114.
Andreas Gross; Jesse C. Little; Hermann F. Fasel. Numerical Investigation of Shock Wave Turbulent Boundary Layer Interactions. 2018 AIAA Aerospace Sciences Meeting 2018, 1 .
AMA StyleAndreas Gross, Jesse C. Little, Hermann F. Fasel. Numerical Investigation of Shock Wave Turbulent Boundary Layer Interactions. 2018 AIAA Aerospace Sciences Meeting. 2018; ():1.
Chicago/Turabian StyleAndreas Gross; Jesse C. Little; Hermann F. Fasel. 2018. "Numerical Investigation of Shock Wave Turbulent Boundary Layer Interactions." 2018 AIAA Aerospace Sciences Meeting , no. : 1.
Mark Agate; Arth Pande; Jesse C. Little; Andreas Gross; Hermann F. Fasel. Active Flow Control of the Laminar Separation Bubble on an Oscillating Airfoil Near Stall. 2018 AIAA Aerospace Sciences Meeting 2018, 1 .
AMA StyleMark Agate, Arth Pande, Jesse C. Little, Andreas Gross, Hermann F. Fasel. Active Flow Control of the Laminar Separation Bubble on an Oscillating Airfoil Near Stall. 2018 AIAA Aerospace Sciences Meeting. 2018; ():1.
Chicago/Turabian StyleMark Agate; Arth Pande; Jesse C. Little; Andreas Gross; Hermann F. Fasel. 2018. "Active Flow Control of the Laminar Separation Bubble on an Oscillating Airfoil Near Stall." 2018 AIAA Aerospace Sciences Meeting , no. : 1.
Improvements in turbine design methods have resulted in the development of blade profiles with both high lift and good Reynolds lapse characteristics. An increase in aerodynamic loading of blades in the low-pressure turbine (LPT) section of aircraft gas turbine engines has the potential to reduce engine weight or increase power extraction. Increased blade loading means larger pressure gradients and increased secondary losses near the endwall. Prior work has emphasized the importance of reducing these losses if highly loaded blades are to be utilized. The present study analyzes the secondary flow field of the front-loaded low-pressure turbine blade designated L2F with and without blade profile contouring at the junction of the blade and endwall. The current work explores the loss production mechanisms inside the LPT cascade. Stereoscopic particle image velocimetry (SPIV) data and total pressure loss data are used to describe the secondary flow field. The flow is analyzed in terms of total pressure loss, vorticity, Q-Criterion, turbulent kinetic energy, and turbulence production. The flow description is then expanded upon using an implicit large eddy simulation (ILES) of the flow field. The Reynolds-averaged Navier–Stokes (RANS) momentum equations contain terms with pressure derivatives. With some manipulation, these equations can be rearranged to form an equation for the change in total pressure along a streamline as a function of velocity only. After simplifying for the flow field in question, the equation can be interpreted as the total pressure transport along a streamline. A comparison of the total pressure transport calculated from the velocity components and the total pressure loss is presented and discussed. Peak values of total pressure transport overlap peak values of total pressure loss through and downstream of the passage suggesting that the total pressure transport is a useful tool for localizing and predicting loss origins and loss development using velocity data which can be obtained nonintrusively.
Philip Bear; Mitch Wolff; Andreas Gross; Christopher R. Marks; Rolf Sondergaard; J. Mitch Wolff. Experimental Investigation of Total Pressure Loss Development in a Highly Loaded Low-Pressure Turbine Cascade. Journal of Turbomachinery 2017, 140, 031003 .
AMA StylePhilip Bear, Mitch Wolff, Andreas Gross, Christopher R. Marks, Rolf Sondergaard, J. Mitch Wolff. Experimental Investigation of Total Pressure Loss Development in a Highly Loaded Low-Pressure Turbine Cascade. Journal of Turbomachinery. 2017; 140 (3):031003.
Chicago/Turabian StylePhilip Bear; Mitch Wolff; Andreas Gross; Christopher R. Marks; Rolf Sondergaard; J. Mitch Wolff. 2017. "Experimental Investigation of Total Pressure Loss Development in a Highly Loaded Low-Pressure Turbine Cascade." Journal of Turbomachinery 140, no. 3: 031003.
Mark Agate; Jesse C. Little; Andreas Gross; Hermann F. Fasel. Oscillatory Plunging Motion Applied to an Airfoil Near Stall. 55th AIAA Aerospace Sciences Meeting 2017, 1 .
AMA StyleMark Agate, Jesse C. Little, Andreas Gross, Hermann F. Fasel. Oscillatory Plunging Motion Applied to an Airfoil Near Stall. 55th AIAA Aerospace Sciences Meeting. 2017; ():1.
Chicago/Turabian StyleMark Agate; Jesse C. Little; Andreas Gross; Hermann F. Fasel. 2017. "Oscillatory Plunging Motion Applied to an Airfoil Near Stall." 55th AIAA Aerospace Sciences Meeting , no. : 1.
Andreas Gross; Hermann Fasel; Michael Gaster. Criterion for Spanwise Spacing of Stall Cells. AIAA Journal 2015, 53, 272 -274.
AMA StyleAndreas Gross, Hermann Fasel, Michael Gaster. Criterion for Spanwise Spacing of Stall Cells. AIAA Journal. 2015; 53 (1):272-274.
Chicago/Turabian StyleAndreas Gross; Hermann Fasel; Michael Gaster. 2015. "Criterion for Spanwise Spacing of Stall Cells." AIAA Journal 53, no. 1: 272-274.
Solar chimney power plants are investigated numerically using ANSYS Fluent and an in-house developed Computational Fluid Dynamics (CFD) code. Analytical scaling laws are verified by considering a large range of scales with tower heights between 1 m (sub-scale laboratory model) and 1000 m (largest envisioned plant). A model with approximately 6 m tower height is currently under construction at the University of Arizona. Detailed time-dependent high-resolution simulations of the flow in the collector and chimney of the model provide detailed insight into the fluid dynamics and heat transfer mechanisms. Both transversal and longitudinal convection rolls are identified in the collector, indicating the presence of a Rayleigh–Bénard–Poiseuille instability. Local separation is observed near the chimney inflow. The flow inside the chimney is fully turbulent.
Hermann Fasel; Fanlong Meng; Ehsan Shams; Andreas Gross. CFD analysis for solar chimney power plants. Solar Energy 2013, 98, 12 -22.
AMA StyleHermann Fasel, Fanlong Meng, Ehsan Shams, Andreas Gross. CFD analysis for solar chimney power plants. Solar Energy. 2013; 98 ():12-22.
Chicago/Turabian StyleHermann Fasel; Fanlong Meng; Ehsan Shams; Andreas Gross. 2013. "CFD analysis for solar chimney power plants." Solar Energy 98, no. : 12-22.
Andreas Gross; Hermann Fasel. Numerical Investigation of Separation Control for Wing Sections. 6th AIAA Flow Control Conference 2012, 1 .
AMA StyleAndreas Gross, Hermann Fasel. Numerical Investigation of Separation Control for Wing Sections. 6th AIAA Flow Control Conference. 2012; ():1.
Chicago/Turabian StyleAndreas Gross; Hermann Fasel. 2012. "Numerical Investigation of Separation Control for Wing Sections." 6th AIAA Flow Control Conference , no. : 1.
Andreas Gross; Hermann Fasel. Numerical Investigation of Separation for Airfoils. 41st AIAA Fluid Dynamics Conference and Exhibit 2011, 1 .
AMA StyleAndreas Gross, Hermann Fasel. Numerical Investigation of Separation for Airfoils. 41st AIAA Fluid Dynamics Conference and Exhibit. 2011; ():1.
Chicago/Turabian StyleAndreas Gross; Hermann Fasel. 2011. "Numerical Investigation of Separation for Airfoils." 41st AIAA Fluid Dynamics Conference and Exhibit , no. : 1.
The laminar-turbulent transition process in supersonic and hypersonic boundary layers was investigated using spatial and temporal Direct Numerical Simulations (DNS). Our previous research indicated that oblique breakdown might be a highly relevant nonlinear mechanism for supersonic boundary layers. However, a nonlinear mechanism would only be relevant for the transition process if this mechanism can lead to fully developed turbulence. Hence, to address this question, the late nonlinear transition regime of a supersonic flat-plate boundary layer at Mach 3 was studied using spatial DNS. These simulations demonstrated that a fully turbulent flow can develop via oblique breakdown. We also investigated the nonlinear disturbance development in a hypersonic boundary layer on a sharp circular cone at Mach 8 using spatial and temporal DNS. It was confirmed in these simulations that fundamental resonance and oblique breakdown are the viable paths to transition in hypersonic boundary layers.
Hermann F. Fasel; Andreas Gross; Clayton Koevary; Andreas Laible; Christina Mayer; Jayahar Sivasubramanian. Numerical Simulation of Transition in Hypersonic Boundary Layers. Numerical Simulation of Transition in Hypersonic Boundary Layers 2011, 1 .
AMA StyleHermann F. Fasel, Andreas Gross, Clayton Koevary, Andreas Laible, Christina Mayer, Jayahar Sivasubramanian. Numerical Simulation of Transition in Hypersonic Boundary Layers. Numerical Simulation of Transition in Hypersonic Boundary Layers. 2011; ():1.
Chicago/Turabian StyleHermann F. Fasel; Andreas Gross; Clayton Koevary; Andreas Laible; Christina Mayer; Jayahar Sivasubramanian. 2011. "Numerical Simulation of Transition in Hypersonic Boundary Layers." Numerical Simulation of Transition in Hypersonic Boundary Layers , no. : 1.
Andreas Gross; Hermann Fasel. Active Flow Control for Airfoil at Low Reynolds Numbers. 39th AIAA Fluid Dynamics Conference 2009, 1 .
AMA StyleAndreas Gross, Hermann Fasel. Active Flow Control for Airfoil at Low Reynolds Numbers. 39th AIAA Fluid Dynamics Conference. 2009; ():1.
Chicago/Turabian StyleAndreas Gross; Hermann Fasel. 2009. "Active Flow Control for Airfoil at Low Reynolds Numbers." 39th AIAA Fluid Dynamics Conference , no. : 1.
Collective Protection (COLPRO) systems provide unencumbered, long term personnel protection and have capability for ingress/egress of personnel as they process out (doff) and into (donn) Individual Protection Equipment (IPE). To enter COLPRO systems, strict processes are enforced to allow safe entry as well as maintain the integrity of the Toxic Free Area (TFA). Normally, personnel would process through an outside Contamination Control Area (CCA) where decontamination crews identify any gross liquid contamination and direct decontamination appropriately. Personnel then carefully remove their outer protective garments, with the exception of the mask, hood, and gloves and enter the protected entrance or Airlock (A). While in the airlock, air purging removes airborne vapor and aerosol contamination, and personnel conduct the final decontamination steps to clean or contain mask, hood, and gloves. This process of moving personnel through a CCA, Airlock, and into a Toxic Free Area will be referred to as the CCA/A/TFA Process. The objective of this CCA/A/TFA Process Analysis is to analyze current procedures, develop a CCA/A/TFA Process model, and make recommendations to provide personnel an acceptable level of protection (contamination level below contamination control limits ) over a specified time interval while maintaining a throughput (personnel processed per time interval) sufficient to meet mission/force protection requirements.
Hermann F. Fasel; Andreas Gross; Wolfgang Balzer. Numerical Investigations of Active Flow Control for Low-Pressure Turbine Blades. Numerical Investigations of Active Flow Control for Low-Pressure Turbine Blades 2008, 1 .
AMA StyleHermann F. Fasel, Andreas Gross, Wolfgang Balzer. Numerical Investigations of Active Flow Control for Low-Pressure Turbine Blades. Numerical Investigations of Active Flow Control for Low-Pressure Turbine Blades. 2008; ():1.
Chicago/Turabian StyleHermann F. Fasel; Andreas Gross; Wolfgang Balzer. 2008. "Numerical Investigations of Active Flow Control for Low-Pressure Turbine Blades." Numerical Investigations of Active Flow Control for Low-Pressure Turbine Blades , no. : 1.
Andreas Gross; Hermann F. Fasel. Control-Oriented Proper Orthogonal Decomposition Models for Unsteady Flows. AIAA Journal 2007, 45, 814 -827.
AMA StyleAndreas Gross, Hermann F. Fasel. Control-Oriented Proper Orthogonal Decomposition Models for Unsteady Flows. AIAA Journal. 2007; 45 (4):814-827.
Chicago/Turabian StyleAndreas Gross; Hermann F. Fasel. 2007. "Control-Oriented Proper Orthogonal Decomposition Models for Unsteady Flows." AIAA Journal 45, no. 4: 814-827.
Andreas Gross; Hermann F. Fasel. Characteristic Ghost Cell Boundary Condition. AIAA Journal 2007, 45, 302 -306.
AMA StyleAndreas Gross, Hermann F. Fasel. Characteristic Ghost Cell Boundary Condition. AIAA Journal. 2007; 45 (1):302-306.
Chicago/Turabian StyleAndreas Gross; Hermann F. Fasel. 2007. "Characteristic Ghost Cell Boundary Condition." AIAA Journal 45, no. 1: 302-306.
A. Gross; Hermann Fasel. Coanda Wall Jet Calculations Using One- and Two-Equation Turbulence Models. AIAA Journal 2006, 44, 2095 -2107.
AMA StyleA. Gross, Hermann Fasel. Coanda Wall Jet Calculations Using One- and Two-Equation Turbulence Models. AIAA Journal. 2006; 44 (9):2095-2107.
Chicago/Turabian StyleA. Gross; Hermann Fasel. 2006. "Coanda Wall Jet Calculations Using One- and Two-Equation Turbulence Models." AIAA Journal 44, no. 9: 2095-2107.
Andreas Gross; Hermann F. Fasel. Numerical Investigation of Low-Pressure Turbine Blade Separation Control. AIAA Journal 2005, 43, 2514 -2525.
AMA StyleAndreas Gross, Hermann F. Fasel. Numerical Investigation of Low-Pressure Turbine Blade Separation Control. AIAA Journal. 2005; 43 (12):2514-2525.
Chicago/Turabian StyleAndreas Gross; Hermann F. Fasel. 2005. "Numerical Investigation of Low-Pressure Turbine Blade Separation Control." AIAA Journal 43, no. 12: 2514-2525.
Dieter Postl; Andreas Gross; Hermann Fasel. Numerical Investigation of Low Pressure Turbine Blade Separation Control. 41st Aerospace Sciences Meeting and Exhibit 2003, 1 .
AMA StyleDieter Postl, Andreas Gross, Hermann Fasel. Numerical Investigation of Low Pressure Turbine Blade Separation Control. 41st Aerospace Sciences Meeting and Exhibit. 2003; ():1.
Chicago/Turabian StyleDieter Postl; Andreas Gross; Hermann Fasel. 2003. "Numerical Investigation of Low Pressure Turbine Blade Separation Control." 41st Aerospace Sciences Meeting and Exhibit , no. : 1.