Optical-flow-based background-oriented schlieren technique for measuring a laser-induced underwater shock wave

Hayasaka, K.; Tagawa, Yoshiyuki; Liu, Tianshu; Kameda, Masaharu

doi:10.1007/s00348-016-2271-0

Cited by 59 publications

(50 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The maximum displacement was about 1 pixel in their BOS system. Based on their work, Hayasaka et al (2016) reconstructed the displacement field using a tomographic method and attained the pressure profile.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Sequential observation of rebound shock wave generated by collapse of vapor bubble in BOS system

Wang

Abe

Nishio

et al. 2018

J Vis

View full text Add to dashboard Cite

The paper reports on a pressure measurement of underwater shock waves generated by collapse of a vapor bubble using the background-oriented schlieren (BOS) technique. In the BOS system, the vapor bubble is induced by an underwater electric discharge. To estimate background-element displacement induced by the underwater shock wave, a spatiotemporal derivative (STD) algorithm is applied in image processing. Furthermore, the accuracy of the STD algorithm is evaluated using the images obtained with our BOS system relative to the cross-correlation method. Subsequently, the pressure distributions are obtained by solving the Poisson equation and applying a filtered-back projection algorithm. An experiment to visualize the behaviors of the underwater shock waves is also carried out using the shadowgraph method. As a result, the pressure waveforms estimated by the BOS technique keep consistent with that in experimental profiles. The pressure attenuations behind the underwater shock wave are also in good agreements with the experimental measurements. It is expected that the BOS technique will probably overcome the problems associated with the conventional method of pressure measurement related to the collapse of microbubbles, and becomes a promising means of quantitatively measuring high-speed phenomena.Keywords Pressure measurement Á Underwater shock wave Á Collapse of vapor bubble Á High-voltage-power supply Á BOS technique Á STD algorithm IntroductionThe concept of the background-oriented schlieren (BOS) was first proposed as a further simplification of the optical schlieren system patented by Meier (1999). The feasibility of the BOS technique was demonstrated by Raffel et al. (2000) and Richard et al. (2001). Raffel et al. (2000) built a BOS system to visualize a fullscale helicopter in flight and investigated the effects of the Reynolds number on vortex developments from the blade tips. They reported that the investigation could be carried out more easily when using the BOS technique, relative to the laser-based techniques. The vortex shedding on a cylinder in a transonic wind

show abstract

mentioning

confidence: 99%

“…Sugii et al (2000) also pointed out that sub-pixel displacement could be accurately evaluated using the STD algorithm. Hayasaka et al (2016) obtained a spatial resolution of per pixel and a better accuracy using an optical flow method based on Liu and Shen (2008).…”

mentioning

confidence: 99%

Sequential observation of rebound shock wave generated by collapse of vapor bubble in BOS system

Wang

Abe

Nishio

et al. 2018

J Vis

View full text Add to dashboard Cite

show abstract

“…Optical flow computation can be conducted in a PC with Matlab to extract velocity fields at a spatial resolution of one vector per a pixel. The optical flow method has been used in some challenging flow measurements in which the traditional cross-correlation method in PIV could not provide sufficient high-resolution velocity fields in large domains [7][8][9][10][11][12]. Although there are research optical flow programs developed by different groups, an easy-to-use open source program is still lacking for non-expert users in various settings of fluid-mechanic applications.…”

Section: (3) Reuse Potentialmentioning

confidence: 99%

“…Physically, the optical flow is proportional to the light-ray-path-averaged velocity of fluid (or particles) weighted in a relevant field quantity like dye concentration, fluid density or particle concentration. The optical flow method has been used to study the flow structures of Jupiter's Great Red Spot (GRS), impinging jets, and laser-induced underwater shock wave [8][9][10][11]. A mathematical analysis of the variational solution of the optical flow and an iterative numerical algorithm are given by Wang et al [12].…”

Section: Introductionmentioning

confidence: 99%

OpenOpticalFlow: An Open Source Program for Extraction of Velocity Fields from Flow Visualization Images

Liu

2017

JORS

Self Cite

View full text Add to dashboard Cite

“…Recently, the BOS has been studied thanks to the recent development of digital cameras. BOS is applicable for compressed air (Venkatakrishnan and Meier 2004), mixed air (Kirmse et al 2011;Tan et al 2015) and underwater shock waves (Yamamoto et al 2015;Hayasaka et al 2016). More recently, Hargather and Settles (2010) proposed the improved BOS technique to visualize the density field of the shock wave induced by gun firing in the air.…”

Section: Introductionmentioning

confidence: 99%

Mobile visualization of density fields using smartphone background-oriented schlieren

Hayasaka

Tagawa

2019

Exp Fluids

Self Cite

View full text Add to dashboard Cite

The conventional background-oriented schlieren (BOS) technique is an image-based technique that can calculate the density field in fluids using two static images [i.e., an undistorted background image (reference image) and a distorted background image due to the density change in fluids (target image)]. This paper proposes the smartphone BOS (SBOS) technique, which offers the measurement of the density gradient using the high-speed imaging feature of the smartphone being carried with a moving observer. The conventional BOS with a fixed camera visualizes the density gradient by comparing the reference image and the target image. In contrast, SBOS can obtain the time difference of the density gradient field. A reference image in SBOS is a target one at a previous time step. The movement of the smartphone is canceled using a registration technique for image accurate alignment. Three demonstrations are conducted to perform SBOS. First, in a static situation, the density field of heated air by a gas burner is visualized by comparing between SBOS and conventional BOS. Second, the local displacement of density field and the error displacement is estimated quantitatively when the smartphone is moving. Third, SBOS using an embossed wallpaper to visualize the density field is performed in the mobile condition. These achievements suggest that SBOS is an effective system to visualize the density field using only the smartphone, and is expected to be a useful tool such as a preliminary experiment in the laboratory and a teaching tool for general smartphone users.

show abstract

Optical-flow-based background-oriented schlieren technique for measuring a laser-induced underwater shock wave

Cited by 59 publications

References 23 publications

Sequential observation of rebound shock wave generated by collapse of vapor bubble in BOS system

Sequential observation of rebound shock wave generated by collapse of vapor bubble in BOS system

OpenOpticalFlow: An Open Source Program for Extraction of Velocity Fields from Flow Visualization Images

Mobile visualization of density fields using smartphone background-oriented schlieren

Contact Info

Product

Resources

About