Numerical Assessment of the Convective Heat Transfer in Rotating Detonation Combustors Using a Reduced-Order Model

The pressure gain across a rotating detonation combustor offers an efficiency rise and potential architecture simplification of compact gas turbine engines. However, the combustor walls of the rotating detonation combustor are periodically swept by both detonation and oblique shock waves at several kilohertz, disrupting the boundary layer, resulting in a rather complex convective heat transfer between the fluid and the solid walls. A computationally fast procedure is presented to calculate this extraordinary convective heat flux along the detonation combustor. First, a numerical model combining a two-dimensional method of characteristics approach with a monodimensional reaction model is used to compute the combustor flow field. Then, an integral boundary layer routine is used to predict the main boundary layer parameters. Finally, an empirical correlation is adopted to predict the convective heat-transfer coefficient to obtain the bulk and local heat flux. The procedure has been applied to a combustor operating with premixed hydrogen-air fuel. The results of this approach compare well with high-fidelity unsteady Reynolds-averaged Navier-Stokes three-dimensional simulations, which included wall refinement in an unrolled combustor. The model demonstrates that total pressure has an important influence on heat flux within the combustor and is less dependent on the inlet total temperature. For an inlet total pressure of 0.5 MPa and an inlet total temperature of 300 K, a peak time-averaged heat flux of 6 MW/m2 was identified at the location of the triple point, followed by a decrease downstream of the oblique shock, to about 4 MW/m2. Maximum discrepancy between the reduced-order model and the high-fidelity solver was 16%, but the present reduced-order model required a computational time of only 200 s, that is, about 7000 times faster than the high-fidelity three-dimensional unsteady solver. Therefore, the present tool can be used to optimize the combustor cooling system

Spartan Daily, September 12, 1984

Volume 83, Issue 9https://scholarworks.sjsu.edu/spartandaily/7195/thumbnail.jp

Design and Simulation of a Wireless SAW-Pirani Sensor with Extended Range and Sensitivity

Pressure is a critical parameter for a large number of industrial processes. The vacuum industry relies on accurate pressure measurement and control. A new compact wireless vacuum sensor was designed and simulated and is presented in this publication. The sensor combines the Pirani principle and Surface Acoustic Waves, and it extends the vacuum sensed range to between 10-4 Pa and 105 Pa all along a complete wireless operation. A thermal analysis was performed based on gas kinetic theory, aiming to optimize the thermal conductivity and the Knudsen regime of the device. Theoretical analysis and simulation allowed designing the structure of the sensor and its dimensions to ensure the highest sensitivity through the whole sensing range and to build a model that simulates the behavior of the sensor under vacuum. A completely new design and a model simulating the behavior of the sensor from high vacuum to atmospheric pressure were established

Regional-scale fault-to-structure earthquake simulations with the EQSIM framework: Workflow maturation and computational performance on GPU-accelerated exascale platforms

Continuous advancements in scientific and engineering understanding of earthquake phenomena, combined with the associated development of representative physics-based models, is providing a foundation for high-performance, fault-to-structure earthquake simulations. However, regional-scale applications of high-performance models have been challenged by the computational requirements at the resolutions required for engineering risk assessments. The EarthQuake SIMulation (EQSIM) framework, a software application development under the US Department of Energy (DOE) Exascale Computing Project, is focused on overcoming the existing computational barriers and enabling routine regional-scale simulations at resolutions relevant to a breadth of engineered systems. This multidisciplinary software development—drawing upon expertise in geophysics, engineering, applied math and computer science—is preparing the advanced computational workflow necessary to fully exploit the DOE’s exaflop computer platforms coming online in the 2023 to 2024 timeframe. Achievement of the computational performance required for high-resolution regional models containing upward of hundreds of billions to trillions of model grid points requires numerical efficiency in every phase of a regional simulation. This includes run time start-up and regional model generation, effective distribution of the computational workload across thousands of computer nodes, efficient coupling of regional geophysics and local engineering models, and application-tailored highly efficient transfer, storage, and interrogation of very large volumes of simulation data. This article summarizes the most recent advancements and refinements incorporated in the workflow design for the EQSIM integrated fault-to-structure framework, which are based on extensive numerical testing across multiple graphics processing unit (GPU)-accelerated platforms, and demonstrates the computational performance achieved on the world’s first exaflop computer platform through representative regional-scale earthquake simulations for the San Francisco Bay Area in California, USA

Childbirth Rhythms and Childbirth Ritual in Early Modern Spain, together with some Comments on the Virtues of Midwives

Childbirth in Early Modern Spain can be viewed as an area where ig­norant midwives and cruel doctors ruled over terrified women who, deprived of all choices, were condemned to passively endure the ordeal of parturition. Medical and judicial sources seem to strengthen this vision.Yet, when we apply Mary Douglas’s theory of ritual, another picture emerges which might be just as valid for wide sections of social experience. Consequently, this article concentrates on the social rhythms of birth. It will touch on relics, the Rose of Jericho, delivery as a shared experience, on birthing positions, role playing and the stories which were brought back to the memory of parturient women, espe­cially those about Saint Mary, imagined as a midwife and a powerful assistant who comes to the rescue of sinners.Doctors from Golden Age Spain, it appears, appreciated the knowledge and skills of midwives. Even though they tried to curtail some rituals and wrote against witchcraft, they did not want to do away with the institution of female midwifery

Separation Dynamics of Air-to-Air Missile and Validation with Flight Data

Prediction of flight characteristics of a store in the vicinity of an aircraft is vitally important for ensuring the safety of the aircraft and effectiveness of the store to meet the mission objective. Separation dynamics of an agile air-to-air-Missile from a fighter aircraft is numerically simulated using an integrated store separation dynamics suite. Chimera cloud of points along with a grid-free Euler solver is used to obtain aerodynamic force on the missile and the force is integrated using a rigid body dynamics code to obtain the missile position. In the present work, the suite is applied to a flight test case and sensitivity of trajectory variables on launch parameters is studied. Further, the results of the suite are compared with the flight data. The predicted body rates and Euler angles of missile compare well with the flight data. 

Retrieving Realism: A Whiteheadian Wager

This essay argues that the organic realism of Alfred North Whitehead (1861-1947) provides a viable alternative to anti-realist tendencies in modern and postmodern philosophy since Descartes. The metaphysical merits of Whitehead’s philosophy of organism are unpacked in conversation with Hubert Dreyfus and Charles Taylor’s recent book Retrieving Realism (2015). Like Dreyfus and Taylor, Whitehead’s philosophical project was motivated by a desire to heal the modern epistemic wound separating soul from world in order to put human consciousness back into meaningful contact with reality. While Dreyfus and Taylor’s book succeeds in articulating the problem cogently, its still too phenomenological answer remains ontologically unsatisfying. Whitehead’s process-relational approach invites philosophy to move closer to a real solution