Name: liquid speed from reservoir outlets
Uploaded: 2026-01-30T03:08:28.000Z
Duration: 1 min 14 s
Channel: JoVE

Freie Düsen zeigen das Verhalten von Flüssigkeiten, das durch die Bernoulli-Gleichung beschrieben wird, wenn die Flüssigkeit eine Düse verlässt und frei in die Luft strömt.
Die Strömungsgeschwindigkeit an der Düse wird durch die Höhe der darüber liegenden Flüssigkeitssäule bestimmt, die potentielle Energie in kinetische Energie umwandelt.
Der Austrittsdruck des Strahls entspricht dem atmosphärischen Druck, und die Geschwindigkeit nimmt zu, wenn das Fluid aus einem großen Reservoir strömt.
Aufgrund der Trägheit des Fluids verengt sich der Strahl kurz vor der Düse und bildet so die kleinste Querschnittsfläche. Dieses Phänomen ist als Vena contracta bekannt.
Das Verhältnis der Fläche des Strahls an der Vena contracta und der Fläche der Düse ergibt den Kontraktionskoeffizienten.
Verschiedene Düsenformen, wie z. B. messerkantige, gut abgerundete, scharfkantige und wiedereintretende Designs, beeinflussen das Strömungsmuster und den Kontraktionskoeffizienten.
Bei der Planung von Systemen wie Überläufen und Wehren wird der Vena-contracta-Effekt für eine genaue Durchflussmessung berücksichtigt.
Freistrahlen sind im Bauwesen von entscheidender Bedeutung, um die Strömung zu kontrollieren und strukturelle Auswirkungen zu minimieren.

freistrahl

Freistrahlen beschreiben den Fluidfluss, der aus einem Reservoir durch eine Öffnung ohne Widerstand in die Atmosphäre austritt. Die Geschwindigkeit (V) des Fluidstrahls wird mithilfe des Bernoulli-Prinzips ermittelt und wie folgt ausgedrückt:

<img alt="Equation 1" src="/files/ftp_upload/18037/18037_Equation_1.svg" style="text-align: center; height: 15px;">

Wobei h die Höhe des Fluids über der Öffnung ist. Diese Gleichung setzt atmosphärischen Druck sowohl an der Reservoiroberfläche als auch am Strahlaustritt voraus. Die Höhe der Fluidsäule bestimmt die Geschwindigkeit des Fluids an der Düse in einem Reservoir, wo die potenzielle Energie des Fluids während des Fließens in kinetische Energie umgewandelt wird.

Das Phänomen der Vena Contracta tritt auf, wenn das Fluid durch eine scharfkantige Öffnung austritt, wodurch der Strahldurchmesser d_j kleiner ist als der Düsendurchmesser d_o. Dies geschieht, weil die Fluidströme den abrupten Kanten nicht folgen können, wodurch ein verengter Strömungsbereich entsteht. Der Kontraktionskoeffizient ist das Verhältnis der Querschnittsfläche des Strahls an der Vena Contracta zur Querschnittsfläche der Düse und quantifiziert den Grad der Strahlkontraktion. Dieser Parameter wird durch die Geometrie der Düse beeinflusst. Verschiedene Designs wie Messerdüsen, scharfkantige, gut abgerundete und einspringende Düsen erzeugen unterschiedliche Strömungsmuster und Kontraktionseigenschaften. Bei einer gut abgerundeten Düse beträgt C_c = 1,0, während scharfe oder messerartige Öffnungen C_c auf etwa 0,61 reduzieren. Einspringende Düsen weisen sogar noch niedrigere Werte auf.

Diese Strömungseigenschaften und Kontraktionseffekte sind bei technischen Anwendungen mit Fluidausstoß von entscheidender Bedeutung, von Behältern bis hin zu Industriedüsen.

Freistrahl

Freie Düsen zeigen das Verhalten von Flüssigkeiten, das durch die Bernoulli-Gleichung beschrieben wird, wenn die Flüssigkeit eine Düse verlässt und frei in die Luft strömt.
Die Strömungsgeschwindigkeit ...

Education

Lehre

JoVE Core

Civil Engineering

Bauingenieurwesen

Unit 1

Einheit 1

Fluid Dynamics

Strömungsmechanik

KEY TERMS AND CONCEPTS

ZENTRALE BEGRIFFE UND KONZEPTE

Free Jet

liquid speed from reservoir outlets

Free jets show how liquid moves after leaving a reservoir through an opening and flowing into the air without resistance. The jet speed is found with Bernoulli’s principle, and it depends on the height of liquid above the opening. This relationship assumes atmospheric pressure at both the reservoir surface and the jet exit.

The liquid column’s height controls the speed at the nozzle because the fluid’s potential energy changes into kinetic energy during flow. As the liquid leaves the reservoir, its motion reflects this energy conversion. This is why a deeper liquid level can produce a faster jet.

A sharp-edged orifice can also cause vena contracta, which is the narrowed region where the jet becomes smaller than the nozzle opening. This happens because the streamlines cannot follow the abrupt edge smoothly. The contraction coefficient measures this narrowing by comparing the jet area at vena contracta with the nozzle area.

Nozzle shape changes the flow pattern and the amount of contraction. Knife-edge, sharp-edge, well-rounded, and re-entrant nozzles each produce different results. For a well-rounded nozzle, the contraction coefficient is 1.0, while sharp or knife-edged openings reduce it to about 0.61, and re-entrant nozzles produce even lower values. These effects matter in engineering systems that discharge liquid from reservoirs and industrial nozzles.

Liquid Speed from Reservoir Outlets

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free jet

Free jets show how liquid moves after leaving a reservoir through an opening and flowing into the air without resistance. The jet speed is found with Bernoulli’s principle, and it depends on the height of liquid above the opening. This relationship assumes atmospheric pressure at both the reservoir surface and the jet exit. The liquid column’s height controls the speed at the nozzle because the fluid’s potential energy changes into kinetic energy during flow. As the liquid leaves the...

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key terms and concepts

Learn how liquid speed from a reservoir depends on height, Bernoulli’s principle, and nozzle shape, including vena contracta and contraction coefficient.

Liquid Speed from Reservoir Outlets | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Liquid Speed from Reservoir Outlets

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