Detecting Transition in Flat Plate Flow With Laser Interferometric Vibrometry (LIV)

Bader, Pascal; Sanz, Wolfgang; Peterleithner, Johannes; Woisetschläger, Jakob; Heitmeir, Franz; Meile, Walter; Brenn, Günter

doi:10.1115/gt2016-56043

Cited by 3 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hot-film measurements were performed, e.g., by Mukund et al [2012], Preston-tube and thermographic measurements by Bader and Sanz [2015a] to investigate the transitional boundary layer. Additionally, Bader et al [2016b] used Laser Interferometric vibrometry (LIV) to predict transition.…”

Section: Introductionmentioning

confidence: 99%

On the capability of transition models to predict relaminarization

Bader

Pieringer

Sanz

2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

Self Cite

View full text Add to dashboard Cite

In flows along solid body surfaces the boundary layer represents the narrow zone between the wall and the free stream where viscous effects are important. Its state of flow (laminar or turbulent) may have strong impact on transport processes like wall friction and heat transfer. These processes influence the efficiency as well as the thermal stress, for example of a turbine blade, and may affect other flow characteristics in a machine as well. Under certain flow conditions (like strong acceleration), a reverse transition or relaminarization from turbulent to laminar can also occur. In this work, this type of process is numerically analyzed in order to see the capability of the the well-known γ-Re θ transition model in predicting relaminarization. The model is used together with the Menter SST turbulence model which are both incorporated in the in-house code LINARS. First, the behavior of the flow during acceleration is analyzed. The results of the present case are compared qualitatively to DNS and measurement results. It is shown, that the transition model successfully predicts relaminarization. Secondly it is found out, which processes inside the boundary layer are triggered by the model allowing us a better understanding how relaminarization is modeled. The objective of this work reaching a better understanding of the model parameters influencing the relaminarization prediction by the γ-Re θ transition model will enable an effective future parameter modification in order to enhance the accuracy of the model.

show abstract

Section: Introductionmentioning

confidence: 99%

On the capability of transition models to predict relaminarization

Bader

Pieringer

Sanz

2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

Self Cite

View full text Add to dashboard Cite

show abstract

“…More recently, hot-film measurements were performed, e.g., by Mukund et al [5], Preston tube and thermographic measurements by Bader and Sanz [6]. Recently, Bader et al [7] used LIV (laser interferometric vibrometry) to identify the transition.…”

mentioning

confidence: 99%

An Investigation of Innovative Experimental and Numerical Techniques to Detect Boundary Layer Transition

Cinciripini¹,

Bader²,

Persico³

et al. 2017

JMEA

View full text Add to dashboard Cite

Different methods to detect boundary layer transition are investigated within the scope of this paper. Laminar and turbulent boundary layers exhibit a significantly different behavior, not only regarding skin friction but also for heat-transfer which affects the blade cooling design. The present work presents a novel and non-intrusive measurement technique to detect the transition, based on acoustic concepts. The reliability of the technique was investigated by means of boundary layer measurements over a flat plate in subsonic flow conditions. After a preliminary assessment with a conventional Preston tube, a row of microphones were installed along the plate to correlate transition pressure fluctuations. To provide a comprehensive representation of the experiment, dedicated measurements with a fast response aerodynamic pressure probe were performed to determine the turbulence intensity and the dissipation rate upstream of the flat plate. The experimental results were systematically compared with calculations performed with three different computational fluid dynamics solvers (ANSYS-Fluent ® , ANSYS-CFX ® , OpenFOAM ® ) and using both the --and thetransition models. Results show a fair agreement between CFD (computational fluid dynamics) predictions and the acoustic technique, suggesting that this latter might represent an interesting alternative option for transition measurements.

show abstract

Experimental Investigation of Boundary Layer Relaminarization in Accelerated Flow

Bader

Pschernig

Sanz

et al. 2018

Journal of Fluids Engineering

View full text Add to dashboard Cite

Flow in turbomachines is generally highly turbulent. Nonetheless, boundary layers may exhibit laminar-to-turbulent transition, and relaminarization of the turbulent flow may also occur. The state of flow of the boundary layer is important since it influences transport phenomena like skin friction and heat transfer. In this paper, relaminarization in accelerated flat-plate boundary-layer flows is experimentally investigated, measuring flow velocities with laser Doppler anemometry (LDA). Besides the mean values, statistical properties of the velocity fluctuations are discussed in order to understand the processes in relaminarization. It is shown that strong acceleration leads to a suppression of turbulence production. The velocity fluctuations in the accelerated boundary layer flow “freeze,” while the mean velocity increases, thus reducing the turbulence intensity. This leads to a laminar-like velocity profile close to the wall, resulting in a decrease of the local skin friction coefficient. Downstream from the section with enforced relaminarization, a rapid retransition to turbulent flow is observed. The findings of this work also describe the mechanism of retransition.

show abstract

Detecting Transition in Flat Plate Flow With Laser Interferometric Vibrometry (LIV)

Cited by 3 publications

References 0 publications

On the capability of transition models to predict relaminarization

On the capability of transition models to predict relaminarization

An Investigation of Innovative Experimental and Numerical Techniques to Detect Boundary Layer Transition

Experimental Investigation of Boundary Layer Relaminarization in Accelerated Flow

Contact Info

Product

Resources

About