page_title: Water tunnel (hydrodynamic)
hierarchical_section_title: Water tunnel (hydrodynamic)
caption_attribution_description: Deutsch: de:Berlin-Mitte, Tiergarten, Müller-Breslau-Straße, Schleuseninsel – Kavitationstunnel der Versuchsanstalt für Wasserbau und Schiffbau English: Cavitation tunnel (hydrodynamic test facility)
context_page_description: A water tunnel is an experimental facility used for testing the hydrodynamic behavior of submerged bodies in flowing water. It functions similar to a recirculating wind tunnel, but uses water as the working fluid, and related phenomena are investigated, such as measuring the forces on scale models of submarines or lift and drag on hydrofoils. Water tunnels are sometimes used in place of wind tunnels to perform measurements because techniques like particle image velocimetry are easier to implement in water. For many cases as long as the Reynolds number is equivalent, the results are valid, whether a submerged water vehicle model is tested in air or an aerial vehicle is tested in water. For low Reynolds number flows, tunnels can be made to run oil instead of water. The advantage is that the increased viscosity will allow the flow to be a faster speed for a lower Reynolds number.
  Whereas in wind tunnels the driving force is usually sophisticated multiblade propellers with adjustable blade pitch, in water and oil tunnels the fluid is circulated with pumps, effectively using a net pressure head difference to move the fluid rather than imparting momentum on it directly.
context_section_description: A water tunnel is an experimental facility used for testing the hydrodynamic behavior of submerged bodies in flowing water.  It functions similar to a recirculating wind tunnel, but uses water as the working fluid, and related phenomena are investigated, such as measuring the forces on scale models of submarines or lift and drag on hydrofoils. Water tunnels are sometimes used in place of wind tunnels to perform measurements because techniques like particle image velocimetry (PIV) are easier to implement in water. For many cases as long as the Reynolds number is equivalent, the results are valid, whether a submerged water vehicle model is tested in air or an aerial vehicle is tested in water. For low Reynolds number flows, tunnels can be made to run oil instead of water. The advantage is that the increased viscosity will allow the flow to be a faster speed (and thus easier to maintain in a stable manner) for a lower Reynolds number.
  Whereas in wind tunnels the driving force is usually sophisticated multiblade propellers with adjustable blade pitch, in water and oil tunnels the fluid is circulated with pumps, effectively using a net pressure head difference to move the fluid rather than imparting momentum on it directly. Thus the return section of water and oil tunnels does not need any flow management; typically it is just a pipe sized for the pump and desired flow speeds. The upstream section of a water tunnels generally consists of a pipe (outlet from the pump) with several holes along its side and with the end open followed by a series of coarse and fine screens to even the flow before the contraction into the test section. Wind tunnels may also have screens before the contraction, but in water tunnels they may be as fine as the screen used in window openings and screen doors.
  Additionally, many water tunnels are sealed and can reduce or increase the internal static pressure, to perform cavitation studies.  These are referred to as cavitation tunnels.
caption: Cavitation tunnel of the Versuchsanstalt für Wasserbau und Schiffbau in Berlin
exif: {"Image Make": "Panasonic", "Image Model": "DMC-FX2", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Ver1.0", "Image DateTime": "2005:04:04 17:13:42", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "416", "Image PrintIM": "[80, 114, 105, 110, 116, 73, 77, 0, 48, 50, 53, 48, 0, 0, 14, 0, 1, 0, 22, 0, ... ]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail Orientation": "Horizontal (normal)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "6804", "Thumbnail JPEGInterchangeFormatLength": "7868", "Thumbnail YCbCrPositioning": "Co-sited", "EXIF ExposureTime": "1/200", "EXIF FNumber": "28/5", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "64", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2005:04:04 17:13:42", "EXIF DateTimeDigitized": "2005:04:04 17:13:42", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "3", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "29/5", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2304", "EXIF ExifImageLength": "1728", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "6652", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0", "EXIF FocalLengthIn35mmFilm": "35", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "None", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal"}