Coupled CFD-CSM Analyses of a Highly Flexible Transport Aircraft by Means of Geometrically Nonlinear Methods

The ever lasting race towards increased efficiency in the aircraft industry has resulted in excessively slender and lightweight airframes. Utilising the anisotropic characteristics of specifically tailored composites is one key driver, enabling structural concepts which were impossible a few decades ago. The results are highly flexible aircraft structures, pushing geometrically linear methods to their limits. One example of such a concept is the Boeing 787 which reaches wing tip displacements of approximately 10 % of the wing half span already during cruise flight. Thus, loads and flight dynamics analyses have to be developed which are accurate in the context of large deflections. By utilising a coupled CFD-CSM analysis in combination with a highly flexible long range jet transport model, this paper aims to establish the groundwork for a high fidelity geometrically nonlinear loads framework. In this publication, a general methodology to compute static manoeuvre cases with deflections of up to 25 % is presented. Furthermore, by computing rigid and elastic polars as well as calculating pull up and push down manoeuvres, the differences between geometrically linear and nonlinear simulations are illustrated with respect to aerodynamic parameters, cut loads, and strains

Novel role of a triglyceride-synthesizing enzyme:DGAT1 at the crossroad between triglyceride and cholesterol metabolism

AbstractAcyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) is a key enzyme in triacylglycerol (TG) biosynthesis. Here we show that genetic deficiency and pharmacological inhibition of DGAT1 in mice alters cholesterol metabolism. Cholesterol absorption, as assessed by acute cholesterol uptake, was significantly decreased in the small intestine and liver upon DGAT1 deficiency/inhibition. Ablation of DGAT1 in the intestine (I-DGAT1−/−) alone is sufficient to cause these effects. Consequences of I-DGAT1 deficiency phenocopy findings in whole-body DGAT1−/− and DGAT1 inhibitor-treated mice. We show that deficiency/inhibition of DGAT1 affects cholesterol metabolism via reduced chylomicron size and increased trans-intestinal cholesterol excretion. These effects are independent of cholesterol uptake at the apical surface of enterocytes but mediated through altered dietary fatty acid metabolism. Our findings provide insight into a novel role of DGAT1 and identify a pathway by which intestinal DGAT1 deficiency affects whole-body cholesterol homeostasis in mice. Targeting intestinal DGAT1 may represent a novel approach for treating hypercholesterolemia

Static and Dynamic Simulations of the Pazy Wing Aeroelastic Benchmark by Nonlinear Potential Aerodynamics and detailed FE Model

The Pazy wing test case is a new benchmark for the investigation of aeroelastic effects at very large deflections. Tip deformations in the order of 50% span were measured in wind tunnel tests which renders this model highly attractive for the validation of numerical aeroelastic methods and tools for geometrically nonlinear, large deflection analyses. In this paper we present static coupling simulations and stability analyses for the Pazy wing for a series of onflow velocities and angles of attack. The numerical approach involves a three-dimensional, geometrically nonlinear potential aerodynamic method coupled to a commercial finite element code in a nonlinear (Lagrangian) solution sequence. This approach allows the use of the full FE structural model of the wing which comprises the (aluminum) spar and a 3D printed rib structure. For the stability analyses, the unsteady vortex lattice model is linearized analytically and combined with the structural model (both in discrete time), and the eigenvalues of the dynamics matrix are calculated (p-method). Results of the nonlinear static coupling simulations are presented for onflow velocities of 30, 40, and 50 m/s. The aeroelastic stability of the wing is investigated about states of large static deflections and shows significant variation as the deflection is increased

Nonlinear Aeroelastic Analyses and Structural Optimization in Aircraft Preliminary Design

The first part of this presentation gives an overview of the methods which are developed at the DLR Institute of Aeroelasticity for high fidelity aeroelastic simulations of High Aspect Ratio Wings (HARW). The benefits of computing maneuver and gust loads with CFD-based methods that account for aerodynamic nonlinearities due to shock motion and flow separation are highlighted. Especially for HARW, the local lift along the span shows high values close to the tip section, which are sensitive to flow separations both at quasi-steady maneuvers with high load factors but also in gust encounter with large gust amplitudes. The second part describes a framework that is used for the structural optimization of highly flexible jet transport aircraft wings with anisotropic materials. Nonlinearities due to geometrically large structural deformations are taken into account by a two-stage approach. First, the structure is optimized using linear aerodynamic and inertia loads as well as linear responses. In the second step, a series of geometrically nonlinear simulations is conducted to ensure that material strains are within the specified limits and no buckling of skins and spars occurs

Generation and Solution of Markov Chains Using MOSES

In this paper the Markov analyzer MOSES (MOdelling, Specification and Evaluation System) and the model description language MOSLANG -- both developed at the Institute for Operating Systems at the University of Erlangen-Nuernberg -- are described using two examples. To evaluate the performance of a computer system the system has to be specified. In this paper the model description language MOSLANG is introduced and applied to some examples. The core of MOSLANG consists of constructs suitable for the specification of the possible states of the system and of RULE constructs which model the state transitions. This specification method is much more compact than other comparable methods and enables the user to specify large systems when he has become familiar with MOSLANG. The Markov analyzer MOSES supports the input of MOSLANG and subsequently creates the Markovian system of equations automatically. For solving this system of equations five different methods are provided. MOSES calculates..