Bora O. Cakir

Vectoflow

In pursuit of advancing the capabilities of ground testing facilities, a complete road map for broadening operational range of the H3 hypersonic blowdown wind tunnel, operated at the von Karman Institute for Fluid Dynamics (VKI), with the addition of a new Mach 5 contoured nozzle is constructed. The main characteristics of the facility are presente...

Ramjet propulsion is often favored for powering supersonic vehicles cruising at speeds exceeding Mach 3. Despite the relatively simple geometric design of these engines compared to turbo-based alternatives, the complex flow physics involved makes their design and optimization challenging. Hence, the design and performance analysis of ramjet engines...

Qualitative and quantitative visualizations of transonic turbomachinery flows provide essential information on compressibility effects on boundary layer development, shock-boundary layer interactions and trailing edge flows. Background Oriented Schlieren (BOS) is a relatively new optical technique that allows capturing density gradient fields throu...

Schlieren imaging has been established as a reliable optical measurement technique for flame visualizations and retrieval of laminar burning velocity information. However, it is off limited capability and adaptability due to the optical configuration of a conventional schlieren setup. In this regard, background oriented schlieren (BOS) provides a...

The oldest and without a doubt one of the most versatile non-intrusive measurement approaches is the schlieren imaging technique. Although they have been used over a century for visualization of flow fields, they are associated with certain drawbacks. In this regard, background oriented schlieren (BOS) provides a unique opportunity to quantitativel...

The coupling between fluid-structure interactions is governed by the pressure distribution over the interaction surface between the fluid and solid domains. The capabilities of non-intrusive optical techniques, such as particle image velocimetry and Lagrangian particle tracking (LPT), have been proven to provide accurate velocity and acceleration i...

Sustainability of future aviation platforms is heavily dependent on the lower emission capabilities of aeroengines which can be addressed by means of utilizing jet fuels of biological origin. Thus, an extensive experimental and numerical investigation campaign utilizing the Triple Annular Research Swirler (TARS) burner is started to understand the...

Qualitative and quantitative visualizations of transonic turbomachinery flows provide essential information on compressibility and Mach number effects on boundary layer development, shock-boundary layer interactions (SBLI) and trailing edge flows. Background Oriented Schlieren (BOS) is a relatively new optical technique that allows capturing unstea...

In recent years, supersonic aviation has regained attention by the research community and industrial actors alike. Certainly, the environmental constraints and hypersonic cruise opportunities add new underexplored dimensions. The MORE &LESS consortium builds upon previous European efforts to develop high-speed civil air transportation by assessing...

Numerical simulation tools and experimental measurement techniques are required to provide accurate description of flow features in application relevant scales and boundary conditions enroute to realizing the design and integration of high-speed arial platforms. A case of 10° wedge exposed to Mach 3.5 supersonic flow at high Reynolds numbers provid...

The degraded resolution and sensitivity characteristics of BOS can be recovered by means of utilizing an optical flow based image processing scheme. However, the background patterns conventionally employed in BOS setups suit the needs of the cross-correlation approach, whereas optical flow is based on a completely different mathematical background....

Conceptual design studies performed with reduced-order approaches allow feasibility and sizing considerations of air-breathing engines to be configured at an affordable computational cost. The present study is devoted to exploring the design space of a dual-mode ramjet engine operating in scramjet mode by means of reduced-order analysis to assess t...

The operational map of the H3 Mach 6 blowdown wind tunnel, at the von Karman Institute for Fluid Dynamics (VKI), is extended towards lower Mach numbers with a new axisymmetric contoured nozzle to achieve Mach 5 testing conditions. Following the design, manufacturing, instrumentation and integration of the Mach 5 nozzle, an extensive commissioning c...

The degraded resolution and sensitivity characteristics of BOS can be recovered by means of utilizing an optical flow based image processing scheme for the displacement detection stage. However, the background patterns conventionally employed in BOS setups suit the needs of the cross-correlation approach, whereas optical flow is associated with a c...

The need for comparative studies between experimental and numerical results exists due to the long lasting necessity for verification and validation. Accordingly, background oriented schlieren (BOS) provides a unique opportunity to perform non intrusive quantification of density varying flows by means of an inexpensive and simple setup. As the opti...

Ramjet propulsion is commonly preferred for powering supersonic vehicles for cruising faster than Mach 3. Although the geometrical layout of these engines is simple compared to turbo-based counterparts, the complexity of flow physics involved with their operation drives design and optimization procedures to be challenging. Accordingly, a design and...

Axisymmetric Busemann intakes are able to perform internal compression of the incoming supersonic/hypersonic flow minimizing total pressure losses, while the circular cross section and the axial flow uniformity achieved at the exit makes this intake suitable for combustors and nozzles of supersonic/hypersonic vehicles. Although its geometry does no...

Optical flow provides an opportunity to elevate the resolution and sensitivity of deflection sensing in background-oriented schlieren (BOS). Despite extensive relevant literature within the field of computer vision, there is a lack of proper quantification of its abilities and limitations with regard to the state-of-the-art BOS experiments. Thus, t...

Scramjet propulsion systems offer seamless operation to the high-speed vehicles along their hypersonic flight phase without carrying on-board oxidizer or any rotating component. To discuss the reliability and feasibility of the entire system and trajectory, it is necessary to perform conceptual design exercises which are based on reduced-order appr...

Three-dimensional Lagrangian Particle Tracking measurements with Hellium Filled Soap Bubbles (HFSB) provide quantitative flow visualizations in large measurement volumes up to the cubic metre scale. However, the instantaneously available fluid information density is severely restricted by the finite spatial resolution of the measurements. Therefore...

The operational map of the H3 Mach 6 blowdown wind tunnel, operated at the von Karman Institute for Fluid Dynamics (VKI), is extended towards lower Mach numbers. The main characteristics of the present wind tunnel facility are first reviewed and their performance restrictions are analyzed. Accordingly, the operating regimes and the corresponding pe...

Ramjet/scramjet propulsion is commonly preferred to power supersonic & hypersonic vehicles for cruising faster than Mach 3. This is an elegant solution owing to the lean architecture which does not embody any rotating parts. Although the geometry of the engine is simple as compared to turbo-based engines, the flow physics through the engine duct is...

Optical flow provides an opportunity to elevate the resolution and sensitivity of deflection sensing in background oriented schlieren (BOS). Despite extensive relevant literature within the field of computer vision, with regards to BOS, there is a lack of proper quantification of its abilities and limitations. Thus, this study performs a comparativ...

Optical flow provides an opportunity to e levate the resolution and s ensitivity of deflection se nsing in background oriented schlieren (BOS). Despite extensive relevant literature within the field of computer v ision, with regards to BOS, there is a lack of proper quantification of its abilities and l imitations. Thus, this study performs a compa...

Ramjet propulsion is commonly preferred to power supersonic and hypersonic vehicles for cruising faster than Mach 3. This is an elegant solution owing to the lean architecture which does not embody any rotating parts. Although the geometry of the engine is simple as compared to turbine based configurations, the flow physics through the engine duct...

The use of experimental data assimilation approaches such as VIC+ enabled dense interpolation of instantaneously scarce, scattered PTV data with prior attempt to investigate the flows in direct contact with physical objects. Thus, in order to handle generic solid body intrusions within the flow fields of VIC+ application, the utilization of Arbitra...

Three-dimensional flow measurements by Particle Tracking Velocimetry (PTV) provide scattered flow information, that often needs to be interpolated onto a regular grid. Therefore, the use of experimental data assimilation approaches such as VIC+ (Schneiders and Scarano, 2016) were proposed to enhance the instantaneously available spatial resolution...

Closure of Collar's triangle represents a complete framework of fluid-structure interactions (FSI) enabling the comprehensive understanding of different design elements compromising aeronautical applications. Experimental methods such as tomographic particle image velocimetry (Tomo-PIV) are proven to provide accurate acquisition opportunities of fl...

Two dimensional numerical assessment of a ramjet intake at different operational con- ditions is conducted to characterize the flow field properties and the resultant performance parameters. The computational stuides are performed on Fluent fluid simulation package of ANSYS with a RANS model. The design condition for the provided ramjet geometry is...

This paper presents the aerodynamic modelling and analysis of surfaces created by a novel deployable mechanism, which is composed of a four-bar linkage and a scissor-structural mechanism (SSM) which contains several scissor-like elements (SLEs). With the help of that mechanism, which is located inside the trailing portion of wing section, continuou...

The immense market demand on the high efficiency and lightweight aero-engines results in designs with compact high-pressure turbine stages experiencing supersonic flow field. In supersonic turbines, shocks appear at the vane trailing edges. The interaction of these shock with the neighbouring airfoils and blades on the adjacent rotor row and conseq...

In this paper, the dynamic force analysis of a novel deployable mechanism, called as scissor-structural mechanism (SSM), for active camber and chord morphing have been presented. The mechanism is created via combination of several scissor-like-elements (SLEs). With a novel kinematic synthesis concept, various types of scissor-like-elements are asse...