DeHNSSo: The Delft Harmonic Navier-Stokes Solver for Nonlinear Stability Problems with Complex Geometric Features

A nonlinear Harmonic Navier-Stokes (HNS) framework is introduced for simulating instabilities in laminar spanwise-invariant shear layers, featuring sharp and smooth wall surface protuberances. While such cases play a critical role in the process of laminar-to-turbulent transition, classical stability theory analyses such as parabolized or local...

Non-Modal Growth Induced by Discrete Roughness Elements in a Swept Wing Boundary Layer: Modelling and Diagnostics

Laminar-to-turbulent boundary layer transition on the wings and stabilizers of aircraft leads to a large increase in the skin-friction drag they experience during flight. This has motivated prolific research into understanding and delaying the transition process, in an effort to improve the economic and ecological impact of air travel. The swept...

Influence of a forward-facing step on crossflow instability and transition: An experimental study in a swept wing boundary-layer

The market growth expected for commercial aviation in the coming decades and the increasing social awareness regarding the effects of global warming are driving significant technological developments necessary for emission reduction in future transport aircraft. From the aerodynamics perspective, a significant increase in aircraft efficiency can...

Boundary-layer instability on rotating cones: An experiment-based exploration

Boundary-layer instability induces spiral vortices on rotating cones. As they grow along the cone, the vortices enhance mixing of high- and low-momentum fluid, and subsequently, cause the boundary-layer to transition into a turbulent state. This transition process is scientifically enticing as it is one of the classical problems in fluid...

Influence of a Wall-Embedded Phononic Crystal on Tollmien-Schlichting Waves

This thesis concerns a numerical investigation for the stabilization (delay of laminar-to-turbulent transition) of ows over a at plate with a meta-unit of a possible metamaterial. The type of instability studied is that due to small disturbances in an incompressible, two-dimensional boundary layer. The linear growth of the disturbance in the...

Cross-Flow Instability Control through Base-Flow Modification using AC-DBD Plasma Actuators: An Experimental Investigation

Following recent proof of swept wing laminar-to-turbulent boundary layer transition delay through base-flow modification using AC-DBD plasma actuators, an experimental investigation is performed to study the responsible physical mechanism. An experiment is conducted on a 45° swept wing in the anechoic wind tunnel at the Delft University of...

Application of Acoustic Metamaterials in Boundary Layer Instability Control

To achieve delay of laminar-to-turbulent transition of boundary layers, the application of acoustic metamaterial concepts is investigated. This is done analytically, numerically and experimentally by studying the interaction between a Helmholtz resonator and a TS wave. A Helmholtz resonator can serve as a meta-atom in a metamaterial. The desired...

Advanced Infrared Thermography Data Analysis for Unsteady Boundary Layer Transition Detection

Advanced data processing methods for detecting unsteady boundary layer transition in periodic aerodynamic processes by means of infrared thermography measurements are presented. The thermal radiation emitted from the heated suction surface of a pitching airfoil model in subsonic flow is measured with an infrared camera. The unsteady boundary...

Unsteady Boundary Layer Transition Measurements with Infrared Thermography: Development of Improved Measurement Schemes

The boundary layer transition location is a crucial design parameter in aerodynamics. The computational prediction of boundary layer transition in engineering applications is typically based on empirical models. These models require experimental measurements for calibration and validation purposes. For unsteady aerodynamic processes, the range...

Cross-Flow Instability: Flow diagnostics and control of swept wing boundary layers

The research presented in this booklet focusses on the cross-flow instability. Applying traditional and advanced flow diagnostics, the boundary layer evolution is studied in detail. The topology and evolution of both primary and secondary instability mechanisms is revealed with unprecedented detail for experimental research paving the way for...

Drag reduction by applying speedstrips on rowing oars

The objective of this study was to determine the advantage of the application of speedstrips to rowing oars for a lightweight single sculler. The research method comprehended three steps: (1) the analysis of the rowing oar movement, (2) the determination of the change in drag and (3) the composition of a rowing model to establish the...

Flow visualization of swept wing boundary layer transition

In this work the flow visualization of the transition pattern occurring on a swept wing in a subsonic flow is presented. This is done by means of fluorescent oil flow technique and boundary layer hot-wire scans. The experiment was performed at Reynolds number of 2:15 . 106 and at angle of attack of -3º. At these conditions, three different flows...

Experimental investigation of re-entry aerodynamic phenomena - Development of non-intrusive ?ow diagnostics in a Ludwieg tube

To further improve the design of hypersonic vehicles so that fully reusable systems become a reality, the detailed understanding of the ?ow ?eld that the vehicle generates is of paramount importance. The thesis deals with the aspects of experimental ?ow research which includes also the ?ow facility and the measurement techniques. First a...

Potential applications of laser anemometry for in-flight measurements

This report concerns the application of laser anemometry for flight testing and other aircraft-related measurements. The laser anemometry technique and previous work in this field are reviewed and applications are described. A comparison of possibilities of laser anemometry with conventional techniques shows some unique advantages of laser...

Boudary layer measurements on a two-dimensional wing with flap

An experiment is described on a wing flap configuration, which was so designed that nowhere flow separations occur, apart from a small laminar separation bubble on the wing nose. The measurements comprise surface-pressure measurements, boundary layer and wake traverses, and surface-flow visualizations. Three angles of attack have been applied...

Reynolds number effects on pressure and normal force distributions along conically pointed circular cylinder at free-stream mach number of 2.3

Pressure measurements have been carried out on 5 stations along a 7.5- caliber conically pointed circular cylinder at a Mach number of 2.3 and Reynolds numbers of 1.2; 4.8 and 11.1 x 106. Pressure distributions have been integrated to produce local normal force coefficients. Some pitot pressure surveys have been performed in the external flow...

Contribution à la transition dans la couche limite

A l'aide de la méthode du ruban vibrant de Schubauer et Klebanoff. on a étudié expérimentalement l'évolution tridimensionnelle d'une perturbation sinusoïdale locale introduite dans une couche limite laminaire. Les distributions de la vitesse moyenne et de l'intensité de la composante axiale de la turbulence, de même que le spectre d'énergie de...