Convective Nonlinearity in Non-Newtonian Fluids

In the limit of infinite yield time for stresses, the hydrodynamic equations for viscoelastic, Non-Newtonian liquids such as polymer melts must reduce to that for solids. This piece of information suffices to uniquely determine the nonlinear convective derivative, an ongoing point of contention in the rheology literature.Comment: 4 page

Front tracking and two dimensional Riemann problems: a conference report

A substantial improvement in resolution has been achieved for the computation of jump discontinuities in gas dynamics using the method of front tracking. The essential feature of this method is that a lower dimensional grid is fitted to and follows the discontinuous waves. At the intersection points of these discontinuities, two-dimensional Riemann problems occur. In this paper we study such two-dimensional Riemann problems from both numerical and theoretical points of view. Specifically included is a numerical solution for the Mach reflection, a general classification scheme for two-dimensional elementary waves, and a discussion of problems and conjectures in this area

Abstract 1

We consider a model for immiscible three-phase (e.g., water, oil, and gas) flow in a porous medium. We allow the relative permeability of the gas phase to exhibit hysteresis, in that it varies irreversibly along two extreme paths (the imbibition and drainage curves) that bound a region foliated by reversible paths (scanning curves). By numerically solving one-dimensional flow problems involving simultaneous and alternating injection of water and gas into a rock core

The impact of a new mid-range aircraft with advanced technologies on air traffic emissions and climate

viation is currently undoubtedly facing the deepest crisis ever. However, the industry is expected to return to its long-term growth trend with or without a certain offset from its historic trend line. Thus, the greening of air transport remains an important challenge, and technological and operational solutions need to be found as soon as possible. This includes the development of aircraft which make use of advanced technologies with improved environmental performance, as investigated in DLR’s project ATLAs. In this study we present research results on emission changes of a new advanced technology mid-range aircraft on fleet and global level and the corresponding implications on climate. The technologies under investigation are CO2-managed cabin, hybrid laminar flow control as well as functional-driven moveables for load alleviation. The approach combines the calculation of emission inventories for various technology combinations with an established climate response model. The results indicate that the implementation of the three mentioned technologies in a new mid-range aircraft with an expected Entry into Sevice in 2028 has the potential to reduce the fuel consumption in a representative airline sub-fleet by up to 7% and to reduce NOx emissions by even up to 12%, depending on how the technologies are combined. As a consequence, the climate impact can be reduced by up to 7.7%, taking the effects from CO2, H2 O, NOx and contrail cirrus into account

Predicting Take-Off Noise, Sonic Boom, and Landing Noise of Supersonic Transport Aircraft Concepts

In 2023, the German Aerospace Center (DLR) has launched the STORMIE (Supersonic Transport Open Research Models and Impact on Environment) project. Focus of the project is the prediction and minimization of environmental and human impacts of civil supersonic transport. Data generated in the project will be used to inform national and European authorities in order to discuss certification standards for supersonic aircraft within the International Civil Aviation Organization’s Committee on Aviation Environmental Protection (CAEP). In order to assess the environmental impacts, representative civil supersonic business-jet and airliner concepts will be designed. This paper will present an overview of past and ongoing activities conducted at DLR to assess and minimize landing and take-off noise as well as the sonic boom of supersonic aircraft. Numerical methods at different levels of fidelity are applied and will be complemented by listening experiments in a later project stage. First noise-related activities within the STORMIE project are summarized