CAD-based shape optimisation of the NASA CRM wing-body intersection using differentiated CAD-kernel

In industrial design existence of a master CAD geometry of a product enables simultaneous multi-disciplinary collaboration. Adjoint CFD methods have become increasingly accepted for aerodynamic shape optimisations due to their low computational cost. However, use of CAD-based parametrisations for aerodynamic gradient-based shape optimisation is not widely used, one reason being that current CAD systems to do not compute derivatives. In this work, we present the automatically differentiated (AD) version of Open Cascade Technology (OCCT) CAD kernel which can provide derivatives with respect to CAD parameters. OCCT is differentiated in block-vector AD mode which significantly reduces the cost for computing the derivatives. This work contains further OCCT extension for NURBS-based optimisation with intersecting patches and a description of the surface mesh movement linked to the change of the intersection line. These techniques are applied to the drag reduction of the NASA Common Research Model via the modification of the intersection between the root fairing and the wing

Coupled Fluid-Structure Simulation for Turbomachinery Blade Rows

A numerical method for the computation of aeroelasticity is presented. Although the emphasis here is on turbomachinery, the method is applicable to a wide variety of problems. A ow solver is coupled to a structural solver by use of a uid-structure interface method. The integration of the three-dimensional unsteady Navier-Stokes equations is performed in the time domain, simultaneously to the integration of a modal three-dimensional struc-tural model. The ow solution is accelerated by using a multigrid method and a parallel multiblock approach. Fluid-structure coupling is achieved by subiteration. The code is formulated to allow application to general, three-dimensional congurations with multi-ple independent structures. The capability of the code to handle rotating blade rows is demonstrated by an application to a transonic fan. I

Revival of the Magnetar PSR J1622-4950: Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100 larger than during its dormant state. The X-ray flux one month after reactivation was at least 800 larger than during quiescence, and has been decaying exponentially on a 111 19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation

О динамических условиях формирования складок в породах Медведковского месторождения строительного камня (Западный склон Салаирского кряжа)

This paper demonstrates the use of adjoint error analysis to improve the order of accuracy of integral functionals obtained from CFD calculations. Using second order accurate finite element solutions of the Poisson equation, fourth order accuracy is achieved for two different categories of functional in the presence of both curved boundaries and singularities. Similarly, numerical results for the Euler equations obtained using standard second order accurate approximations demonstrate fourth order accuracy for the integrated pressure in two quasi-1D test cases, and a significant improvement in accuracy in a two-dimensional case. This additional accuracy is achieved at the cost of an adjoint calculation similar to those performed for design optimization. 1 Introduction In aeronautical CFD, engineers desire very accurate prediction of the lift and drag on aircraft, but they are less concerned with the precise details of the flow field in general, although there is a clear need to underst..

Praesepe - two merging clusters?

A membership catalogue for Praesepe was compiled and split into four mass bins. A contour plot indicates the presence of a subcluster some 3 pc from the centre of the cluster, of approximately 30 M-circle dot. A tidally truncated King profile was fitted to the remainder of the cluster and the tidal radius is found to be 12.1 pc; the mass of the cluster (excluding the subcluster) is 630 M-circle dot. From the calculated velocity dispersions we find that the cluster appears to have too much kinetic energy and should be rapidly disintegrating. X-ray data suggest that there may be an age spread between the main core stars and the subcluster stars. This leads us to the conclusion that Praesepe is two merging clusters.Peer reviewe

Adjoint and defect error bounding and correction for functional estimates

We present two error estimation approaches for bounding or correcting the error in functional estimates such as lift or drag. Adjoint methods quantify the error in a particular output functional that results from residual errors in approximating the solution to the partial differential equation. Defect methods can be used to bound or reduce the error in the entire solution, with corresponding improvements to functional estimates. Both approaches rely on smooth solution reconstructions and may be used separately or in combination to obtain highly accurate solutions with asymptotically sharp error bounds. The adjoint theory is presented for both smooth and shocked problems; numerical experiments confirm fourth-order error estimates for a pressure integral of shocked quasi-1D Euler flow. By employing defect and adjoint methods together and accounting for errors in approximating the geometry, it is possible to obtain functional estimates that exceed the order of accuracy of the discretization process and the reconstruction approach. Superconvergent drag estimates are obtained for subsonic Euler flow over a lifting airfoil. © 2004 Elsevier Inc. All rights reserved