A new rocket engine concept is proposed based on a transverse engine combustor. This transverse combustor design is modeled using CFD. In particular, DNS and LES are utilized to simulate reacting flows of fuel and oxidizer pairs. Conventional rocket engine designs incorporate an axial flow with many small nozzles. The proposed engine injects fluid propellent transverse to the dominant flow direction with two nozzles, one for each of the two reactants. Mixing is achieved with large, counter rotating vortices. This new configuration is anticipated to be less expensive to manufacture, lighter, and more reliable than existing designs.

The physics behind the transitions of natural Samaras, or the bio-inspired counterparts, to steady autorotation has been unclear. Theoretical and experimental investigations explore the inertial and aerodynamic characteristics required to guarantee stable transitions of an artificial Samara-like decelerator from chaotic tumbling motions to azimuthal autorotation. A non-dimensional inertial criterion is proposed, which is in accord with experiments.

A simple model of the hypersonic boundary layer is proposed. There are three assumptions: The mean velocity profile is linear, the total enthalpy is uniform, and turbulent transport is controlled by sonic eddies, whose rotational Mach number is unity. The model predicts that turbulent transport is slowest at the outer edge of the layer, consistent with the formal assumption of a linear velocity profile. The concentration profile of any conserved scalar is uniform across

This paper presents an experimental aerodynamic performance evaluation of serrated trailing edge wings. Serrated trailing edges not only affect wing lift and drag, but also may reduce overall wing weight when compared to a straight trailing edge. Studied serration topologies included triangular, quadratic bird feather-like, and quadratic membrane-like geometries. A rectangular flat plate was used as a wing platform baseline. The outcome of this research was to identify the most promising serrated configurations based on CL/CD results. The wings were tested on two small wind tunnels where their aerodynamic performances were assessed. Results and most suitable serrated trailing edge topologies were presented and discussed.

The effects of Mach number on the skin friction and velocity fluctuations of the turbulent boundary layer are considered through a sonic eddy model. Originally proposed for free shear flows, the model assumes that the eddies responsible for momentum transfer have a rotation Mach number of unity, with the entrainment rate limited by acoustic signaling. Under this assumption, the model predicts that the skin friction coefficient should go as the inverse Mach number in a regime where the Mach number is larger than unity but smaller than the square root of the Reynolds number. The velocity fluctuations normalized by the friction velocity should be the inverse square root of the Mach number in the same regime. Turbulent transport is controlled by acoustic signaling. The density field adjusts itself such that the Reynolds stresses correspond to the momentum transport. In contrast, the conventional van Driest–Morkovin view is that the Mach number effects are due to density variations directly. A new experiment or simulation is proposed to test this model using different gases in an incompressible boundary layer, following the example of Brown and Roshko in the free shear layer.

Fire is an integral component of ecosystems globally and a tool that humans have harnessed for millennia. Altered fire regimes are a fundamental cause and consequence of global change, impacting people and the biophysical systems on which they depend. As part of the newly emerging Anthropocene, marked by human-caused climate change and radical changes to ecosystems, fire danger is increasing, and fires are having increasingly devastating impacts on human health, infrastructure, and ecosystem services. Increasing fire danger is a vexing problem that requires deep transdisciplinary, trans-sector, and inclusive partnerships to address. Here, we outline barriers and opportunities in the next generation of fire science and provide guidance for investment in future research. We synthesize insights needed to better address the long-standing challenges of innovation across disciplines to (i) promote coordinated research efforts; (ii) embrace different ways of knowing and knowledge generation; (iii) promote exploration of fundamental science; (iv) capitalize on the "firehose" of data for societal benefit; and (v) integrate human and natural systems into models across multiple scales. Fire science is thus at a critical transitional moment. We need to shift from observation and modeled representations of varying components of climate, people, vegetation, and fire to more integrative and predictive approaches that support pathways toward mitigating and adapting to our increasingly flammable world, including the utilization of fire for human safety and benefit. Only through overcoming institutional silos and accessing knowledge across diverse communities can we effectively undertake research that improves outcomes in our more fiery future.

This paper presents an experimental study on vortex flow manipulations using air injection. Ports or nozzles were placed along the leading edge of trapezoidal vortex generators (VGs) to inject air into the external flow. The VGs with the hollowed structure were fabricated via 3d printing methods producing an integral device. Two different types of outlet shapes under different injection pressures were studied: (i) round injectors and (ii) trapezoidal injectors with rectangular outlets. The VGs were mounted and tested in small wind tunnel. To determine the position of the generated vortex, an automated traverse system was used to map the dynamic pressure downstream of the VG. It was found that the active VG air injection system can move the vortex close to the wall or away from it depending on the nozzle type, injection point as well as the applied air pressure.

This paper presents an experimental study on the interaction of the flow from a vortex generator (VG) with slots. The experiments were performed in a mini wind tunnel at the University of Washington with a free stream velocity of 7 m/s. A delta-type winglet vortex generator with a slot cut in the middle was mounted on the surface of the wind tunnel and angled to the free stream to generate a vortex. The angle of attack of the VG ranged from 15deg-30deg in 5deg increments. In order to analyze the strength of the resulting flow, a pitot tube was placed downstream the VG to measure the dynamic pressure field of the vortex. The experimental results reveal that a VG with a slot cut at a suitable location could increase the circulation and the heat transfer of the vortex in a specific region. This phenomenon is probably due to the favorable interaction of slot jet flow and the VG vortex where an increase of circulation of the vortex corresponds to an increase of heat transfer enhancement

The flame length of a plume in incompressible cross-flow is analyzed and the results are compared with those obtained in a chemically reacting water tunnel experiment. It is argued that the axial vortex pair in the flow arises from the plume momentum normal to the free stream, the momentum flux being equivalent to the impulse from the buoyant force.

A rotating detonation engine with two unique features, a wave generator and radial injection of fuel and oxidizer, has been designed and tested. The wave generator, consisting of a number of equidistant, circumferentially placed spark plugs, emitted phased sparks to produce free radicals in specified circumferential sequence. This prompted the detonation waves to spin in the specified direction. The detonation waves were initiated quickly, reached a self-sustained state, and maintained orderly spin for the duration of the test. The repeatability of the experiments enabled systematic studies of various controlling parameters, the characterization of orderly structure of detonation waves, and the clarification of the role of acoustic waves. In contrast, a single spark was found to induce two counter-rotating waves, which persisted for the entire experiment. The second feature, radial propellant injection from sparsely distributed holes, enabled the control of the mixing rate of fuel and oxidizer to regulate the axial location of detonation zones. Oblique shock waves emanating from the detonation wave fronts were found to reach the front-end wall, and the corresponding static pressure measurements found that the front-end wall pressure was insensitive to the variations in backpressure during stable rotating detonation engine operation, confirming the presence of supersonic axial exhaust flow.

The recent advances of additive manufacturing are opening the doors for the development of novel applications in the aerospace field. One area of particular interest is the development and fabrication of multifunctional systems on aerospace systems. Here, printed electronics have been used to add new functions such as sensing and acting onto novel 3D printed aircraft structural designs. The combination of both additive manufacturing techniques allows the fabrication of highly integrated vehicles such as unmanned aircraft vehicles (UAVs), drones, and aerodynamic wind tunnel models at low cost. In this paper, we present the development and fabrication of several multifunctional systems such as ice protection systems, structural health monitoring, and sensing surfaces among others deposited over 3D printed structures. In particular, we will discuss processing and manufacturing conditions for the development of aircraft wind tunnel models. This work has been funded by the U.S. Air Force Research Laboratory to demonstrate technology maturity as well as feasibility and viability of printed electronics for flying applications.

A simple model of the flowfield induced by an inclined jet into an incompressible crossflow is proposed. In general, such a jet generates an asymmetric pair of vortices, with a larger one farther from the wall. The model accounts for the influence of the jet pitch angle beta (with respect to the wall), skew angle (with respect to the freestream direction), and velocity ratio r (the jet velocity to the freestream velocity) on the jet trajectory in the transverse plane in the far field. From the model, the increase of the jet penetration and the circulation of the large vortex in the transverse plane to the downstream distance x obeys to the same one-third law in the case of normal transverse jet. Data from the literature are normalized and compared to the model. Although there is considerable scatter, the normalized data are generally in accord with the predictions of the model. However, for low velocity ratios <= 1.0 when skew angle is near 90 deg, the effect of jet entrainment, and the effect of the horseshoe and wake vortices, may create a low-pressure region on the wall and hence alter the jet trajectory and influence the circulation.

Magma mixing is widely recognized as a means of producing compositional diversity and preconditioning magmas for eruption. However, the processes and associated time scales that produce the commonly observed expressions of magma mixing are poorly understood, especially under crystal-rich conditions. Here we introduce and exemplify a parameterized method to predict the characteristic mixing time of crystals in a crystal-rich magma mush that is subject to open-system reintrusion events. Our approach includes novel numerical simulations that resolve multiphase particle-fluid interactions. It also quantifies the crystal mixing by calculating both the local and system-wide progressive loss of the spatial correlation of individual crystals throughout the mixing region. Both inertial and viscous time scales for bulk mixing are introduced. Estimated mixing times are compared to natural examples and the time for basaltic mush systems to become well mixed can be on the order of 10 days.