Simulation of 2-dimensional viscous flow through cascades using a semi-elliptic analysis and hybrid C-H grids

A semi-elliptic formulation, termed the interacting parabolized Navier-Stokes (IPNS) formulation, is developed for the analysis of a class of subsonic viscous flows for which streamwise diffusion is neglible but which are significantly influenced by upstream interactions. The IPNS equations are obtained from the Navier-Stokes equations by dropping the streamwise viscous-diffusion terms but retaining upstream influence via the streamwise pressure-gradient. A two-step alternating-direction-explicit numerical scheme is developed to solve these equations. The quasi-linearization and discretization of the equations are carefully examined so that no artificial viscosity is added externally to the scheme. Also, solutions to compressible as well as nearly compressible flows are obtained without any modification either in the analysis or in the solution process. The procedure is applied to constricted channels and cascade passages formed by airfoils of various shapes. These geometries are represented using numerically generated curilinear boundary-oriented coordinates forming an H-grid. A hybrid C-H grid, more appropriate for cascade of airfoils with rounded leading edges, was also developed. Satisfactory results are obtained for flows through cascades of Joukowski airfoils

Analysis of two-dimensional incompressible flow past airfoils using unsteady Navier-Stokes equations

The conservative form of the unsteady Navier-Stokes equations in terms of vorticity and stream function in generalized curvilinear coordinates are used to analyze the flow structure of steady separation and unsteady flow with massive separation. The numerical method solves the discretized equations using an ADI-BGE method. The method is applied to a symmetric 12 percent thick Joukowski airfoil. A conformal clustered grid is generated; several 1-D stretching transformations are used to obtain a grid that attempts to resolve many of the multiple scales of the unsteady flow with massive separation, while maintaining the transformation metrics to be smooth and continuous in the entire flow field. Detailed numerical results are obtained for three flow configurations (1) Re = 1000, alpha = 5 deg., (2) Re =1000, alpha = 15 deg., (3) Re = 10,000, alpha = 5 deg. No artificial dissipation was added; however, lack of a fine grid in the normal direction has presently led to results which are considered qualitative, especially for case (3)

Simulation of self-induced unsteady motion in the near wake of a Joukowski airfoil

The unsteady Navier-Stokes analysis is shown to be capable of analyzing the massively separated, persistently unsteady flow in the post-stall regime of a Joukowski airfoil for an angle of attack as high as 53 degrees. The analysis has provided the detailed flow structure, showing the complex vortex interaction for this configuration. The aerodynamic coefficients for lift, drag, and moment were calculated. So far only the spatial structure of the vortex interaction was computed. It is now important to potentially use the large-scale vortex interactions, an additional energy source, to improve the aerodynamic performance

Boundary-fitted coordinates for regions with highly curved boundaries and reentrant boundaries

A procedure was developed using the differential equation approach for generating boundary fitted coordinates for regions with highly curved boundaries as well as reentrant boundaries, such as those encountered in breaking surface waves. The resulting coordinates are nearly orthogonal and can provide adequate resolution even in the reentrant region. Consistent treatment of end boundaries and the use of a systematic initialization scheme and advanced implicit numerical solution techniques make the procedure highly efficient. The method developed for implicit enforcement of the periodicity boundary condition should be beneficial in the analysis of turbomachinery flow applications

Laminar mixing of heterogeneous axisymmetric coaxial confined jets Final report

Laminar mixing of heterogeneous axisymmetrical coaxial confined jets for application to nuclear rocket propulsio

Characterization of dynamic stall phenomenon using two-dimensional unsteady Navier-Stokes equations

Among the new significant aspects of the present work are: (1) the treatment of the far-field boundary; (2) the use of C-grid topology, with the branch-cut singularity treated analytically; (3) evaluation of the effect of the envelope of prevailing initial states, and finally; (4) the ability to employ streakline/pathline 'visualization' to probe the unsteady features prevailing in vortex-dominated flows. The far-field boundary is placed at infinity, using appropriate grid stretching. This contributes to the accuracy of the solutions, but raised a number of important issues which needed to be resolved; this includes determining the equivalent time-dependent circulation for the pitching airfoil. A secondary counter-clockwise vortex erupts from within the boundary layer and immediately pinches off the energetic leading-edge shear layer which then, through hydrodynamic instability, rolls up into the dynamic stall vortex. The streakline/pathline visualization serves to provide information for insight into the physics of the unsteady separated flow

Excessive antigen reactivity may underlie the clinical aggressiveness of chronic lymphocytic leukemia stereotyped subset #8

Subset #8 is a distinctive subset of patients with chronic lymphocytic leukemia (CLL) defined by the expression of stereotyped IGHV4-39/IGKV1(D)-39 B-cell receptors. Subset #8 patients experience aggressive disease and exhibit the highest risk for Richter transformation among all CLL. In order to obtain biological insight into this behavior, we profiled the antigen reactivity and signaling capacity of subset #8 vs other clinically aggressive stereotyped subsets, namely subsets #1 and #2. Twenty-seven monoclonal antibodies (mAbs) from subsets #1, #2, and #8 CLL clones were prepared as recombinant human immunoglobulin G1 and used as primary antibodies in enzyme-linked immuno-sorbent assays against representatives of the major classes of established antigenic targets for CLL. Subset #8 CLL mAbs exhibited broad polyreactivity as they bound to all antigens tested, in clear contrast with the mAbs from the other subsets. Antigen challenge of primary CLL cells indicated that the promiscuous antigen-binding activity of subset #8 mAbs could lead to significant cell activation, again in contrast to the less responsive CLL cells from subsets #1 and #2. These features constitute a distinctive profile for CLL subset #8, supporting the existence of distinct mechanisms of aggressiveness in different immunogenetic subsets of CLL

Multiband Photometry Evolution in the First Weeks of SN 2023ixf, a possible II-L Subtype Supernova

Multiband photometric observations and their evaluation to instrumental magnitudes were performed using standard Johnson-Cousins filters (B, V, Rc) as well r and g Sloan filters, and not standard ones (R, G, B, and Clear filters). These were recorded from 9 observatories and from the MicroObservatory Robotic Telescope Network. The results describe the rapid ascent towards the maximum (2.5 magnitudes about in five days in the B filter) and the slow decrease after the maximum (0.0425 +/- 0.02 magnitudes/day in the B filter). The results highlight the strong variation of the B-V colour indices during the first 50 days (from -0.20 +/- 0.02 to +0.85 +/- 0.02) and V-R (from 0 +/- 0.01 to +0.50 +/- 0.01) after the explosion, presumably corresponding to the cooling of the stellar photosphere. At 50 days after the explosion the magnitude decrease from the maximum was observed to continue where it faded by 2.5 magnitudes (B filter), thus we propose SN 2023ixf is a Type II, subtype L, supernova (SNe)

Comparison of Setup Accuracy and Efficiency Between the Klarity System and BodyFIX System for Spine Stereotactic Body Radiation Therapy

BACKGROUND: Spine stereotactic body radiation therapy (SBRT) uses highly conformal dose distributions and sharp dose gradients to cover targets in proximity to the spinal cord or cauda equina, which requires precise patient positioning and immobilization to deliver safe treatments. AIMS: Given some limitations with the BodyFIX system in our practice, we sought to evaluate the accuracy and efficiency of the Klarity SBRT patient immobilization system in comparison to the BodyFIX system. METHODS: Twenty-three patients with 26 metastatic spinal lesions (78 fractions) were enrolled in this prospective observational study with one of two systems - BodyFIX (n = 11) or Klarity (n = 12). All patients were initially set up to external marks and positioned to match bony anatomy on ExacTrac images. Table corrections given by ExacTrac during setup and intrafractional monitoring and deviations from pre- and posttreatment CBCT images were analyzed. RESULTS: For initial setup accuracy, the Klarity system showed larger differences between initial skin mark alignment and the first bony alignment on ExacTrac than BodyFIX, especially in the vertical (mean [SD] of 5.7 mm [4.1 mm] for Klarity vs. 1.9 mm [1.7 mm] for BodyFIX, p-value \u3c 0.01) and lateral (5.4 mm [5.1 mm] for Klarity vs. 3.2 mm [3.2 mm] for BodyFIX, p-value 0.02) directions. For set-up stability, no significant differences (all p-values \u3e 0.05) were observed in the maximum magnitude of positional deviations between the two systems. For setup efficiency, Klarity system achieved desired bony alignment with similar number of setup images and similar setup time (14.4 min vs. 15.8 min, p-value = 0.41). For geometric uncertainty, systematic and random errors were found to be slightly less with Klarity than with BodyFIX based on an analytical calculation. CONCLUSION: With image-guided correction of initial alignment by external marks, the Klarity system can provide accurate and efficient patient immobilization. It can be a promising alternative to the BodyFIX system for spine SBRT while providing potential workflow benefits depending on one\u27s practice environment

Observing muon decays in water Cherenkov detectors at the Pierre Auger Observatory

Muons decaying in the water volume of a Cherenkov detector of the Pierre Auger Observatory provide a useful calibration point at low energy. Using the digitized waveform continuously recorded by the electronics of each tank, we have devised a simple method to extract the charge spectrum of the Michel electrons, whose typical signal is about 1/8 of a crossing vertical muon. This procedure, moreover, allows continuous monitoring of the detector operation and of its water level. We have checked the procedure with high statistics on a test tank at the Observatory base and applied with success on the whole array.Comment: 4 pages, 2 figures, proceedings of the 29th ICRC Pune, Indi