Acoustic measurements from a rotor blade-vortex interaction noise experiment in the German-Dutch Wind Tunnel (DNW)

Acoustic data are presented from a 40 percent scale model of the 4-bladed BO-105 helicopter main rotor, measured in the large European aeroacoustic wind tunnel, the DNW. Rotor blade-vortex interaction (BVI) noise data in the low speed flight range were acquired using a traversing in-flow microphone array. The experimental apparatus, testing procedures, calibration results, and experimental objectives are fully described. A large representative set of averaged acoustic signals is presented

Computation of incompressible, three-dimensional turbulent boundary layers and comparison with experiment

Incompressible three dimensional, turbulent boundary layer (3DTBL) experiments were simulated numerically by integrating the boundary layer equations together with an algebraic eddy viscosity turbulence model. For the flow treated, the downstream portion, where the crossflow was large, was not predicted with the present computational method; the flow was significantly influenced by elliptic flow field effects. Departures from the boundary layer concept are indicated. Calculations agreed reasonably well with the mean flow development up to separation. In one experiment the normal pressure gradients were found to be neligible in regions with large skewing and allowed testing turbulence models using the boundary layer equations. The simulation of this flow compared favorably with the experimental data throughout the flow field and suggested the applicability of algebraic eddy viscosity models for 3DTBLs

Aerothermodynamic Assessment of Corrugated Panel Thermal Protection Systems

The feasibility of using corrugated panels as a thermal protection system for an advanced space transportation vehicle was investigated. The study consisted of two major tasks: development of improved correlations for wind tunnel heat transfer and pressure data to yield design techniques, and application of the design techniques to determine if corrugated panels have application future aerospace vehicles. A single-stage-to-orbit vehicle was used to assess advantages and aerothermodynamic penalties associated with use of such panels. In the correlation task, experimental turbulent heat transfer and pressure data obtained on corrugation roughened surfaces during wind tunnel testing were analyzed and compared with flat plate data. The correlations and data comparisons included the effects of a large range of geometric, inviscid flow, internal boundary layer, and bulk boundary layer parameters in supersonic and hypersonic flow

Regulatory solvency prediction in property-liability insurance: risk-based capital, audit ratios, and cash flow simulation

This paper analyzes the accuracy of the principal models used by U.S. insurance regulators to predict insolvencies in the property-liability insurance industry and compares these models with a relatively new solvency testing approach--cash flow simulation. Specifically, we compare the risk-based capital (RBC) system introduced by the National Association of Insurance Commissioners (NAIC) in 1994, the FAST (Financial Analysis and Surveillance Tracking) audit ratio system used by the NAIC, and a cash flow simulation model developed by the authors. Both the RBC and FAST systems are static, ratio-based approaches to solvency testing, whereas the cash flow simulation model implements dynamic financial analysis. Logistic regression analysis is used to test the models for a large sample of solvent and insolvent property-liability insurers, using data from the years 1990-1992 to predict insolvencies over three-year prediction horizons. We find that the FAST system dominates RBC as a static method for predicting insurer insolvencies. Further, we find the cash flow simulation variables add significant explanatory power to the regressions and lead to more accurate solvency prediction than the ratio-based models taken alone.Insurance industry

The NASA Langley laminar-flow-control experiment on a swept, supercritical airfoil - Drag equations

The Langley Research Center has designed a swept, supercritical airfoil incorporating Laminar Flow Control for testing at transonic speeds. Analytical expressions have been developed and an evaluation made of the experimental section drag, composed of suction drag and wake drag, using theoretical design information and experimental data. The analysis shows that, although the sweep-induced boundary-layer crossflow influence on the wake drag is too large to be ignored and there is not a practical method for evaluating these crossflow effects on the experimental wake data, the conventional unswept 2-D wake-drag computation used in the reduction of the experimental data is at worst 10 percent too high

Liveness-Driven Random Program Generation

Randomly generated programs are popular for testing compilers and program analysis tools, with hundreds of bugs in real-world C compilers found by random testing. However, existing random program generators may generate large amounts of dead code (computations whose result is never used). This leaves relatively little code to exercise a target compiler's more complex optimizations. To address this shortcoming, we introduce liveness-driven random program generation. In this approach the random program is constructed bottom-up, guided by a simultaneous structural data-flow analysis to ensure that the generator never generates dead code. The algorithm is implemented as a plugin for the Frama-C framework. We evaluate it in comparison to Csmith, the standard random C program generator. Our tool generates programs that compile to more machine code with a more complex instruction mix.Comment: Pre-proceedings paper presented at the 27th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur, Belgium, 10-12 October 2017 (arXiv:1708.07854

Modelling of Bulk Material Flow Properties

Flow property testing is important in the design of handling equipment for bulk solids and the Jenike shear tester is a common and reliable method for ensuring flow from hoppers under the force of gravity alone. The Jenike shear test procedure has various stages and is known to have issues with operator dependency, questions have also been raised regarding the stress state within the shear cell. Currently the data for high pressure flow functions, which are applicable to large capacity storage facilities, are extrapolated from low pressure test data using a 3-parameter equation. Very little literature is provided to support the use of the 3-parameter equation and most shear testing devices are limited to major consolidation stresses of 100 kPa

The Study of the Resistance and Stability of Vegetation Ecosystem Plant Groupings in Flood Control Channels: Vol. 1

Preface: The following report was prepared by the utah Water Research Laboratory of Utah State University in Logan, Utah. Volume 1 of the UWRL report USU--400A contains the data summary and conclusions of flow tests conducted with different plant types and ecosystem groupings of shrubs and woody vegetation in the hydraulics flumes of Utah State University. The methodology and equations that were developed to predict flow resistance for fultiple plant types include the effects of plant fexibility, varying plant density, plant characteristics, and multiple plant stems. The study included over 214 flow tests, testing of 20 different plant types, 5 different combinations or groupings of plants, and the measurements of flow resistance, plant drag forces, velocity profiles, and shear stress. The analysis and development included a comparison with the methods of other researchers and a comparison with field data collected from several river systems. A detail example is presented to demonstrate an iterative solution for determingin flow depth and resistance of a flood plain with several types of plant cover. Volume 2 of the UWRL report USU-400B contains the test data from the two phases of large flume testing (Appendix A and B), the test data from the sectional flume testing (Appendix D), and a discussion of Compound Flood Channels (Appendix E)