MARITIME – TIDE & TIDAL TREAM CALCULATOR
Seiches Period
A precise tool.
What is the Seiches Period & How does it work?
Seiches are standing wave oscillations that develop in semi‑enclosed water bodies such as lakes, bays, or fjords when the water surface is displaced and then allowed to rebound under gravity. The restoring force is provided by gravity acting on the displaced water column, while the basin geometry determines the natural resonant frequencies. For a rectangular basin of length L and uniform depth h, the fundamental (lowest‑frequency) seiche period can be derived from the shallow‑water wave speed c = sqrt{g h}. The wave travels to the opposite end and back, covering a distance of 2L, so the period is T = 2L / c. Higher‑order modes have periods reduced by the integer mode number n, giving T_n = 2L / (nsqrt{g h}). Accurate prediction of seiche periods is important for navigation, coastal engineering, and hazard assessment, because resonant oscillations can amplify water level fluctuations and affect currents, especially in narrow straits and harbors. By measuring basin dimensions and depth, the simple analytical expression provides a quick estimate of the natural oscillation period.
T = frac{2L}{nsqrt{g h}}
T = period (s), L = basin length (m), n = mode number (dimensionless), g = gravitational acceleration (m/s^2), h = average depth (m)
Parameters
Result
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Frequently Asked Questions
What is a seiche?
A seiche is a standing wave oscillation that occurs in semi-enclosed bodies of water like lakes or bays.
How do you calculate the fundamental seiche period for a rectangular basin?
The fundamental seiche period can be calculated using the formula T = 2L / c, where L is the length of the basin and c is the shallow-water wave speed.
What factors determine the natural resonant frequencies of a seiche?
The natural resonant frequencies of a seiche are determined by the geometry of the water body, particularly its depth and shape.
Can you explain the restoring force in a seiche?
The restoring force in a seiche is provided by gravity acting on the displaced water column, causing it to oscillate back and forth.
What is the shallow-water wave speed (c) used in seiche calculations?
The shallow-water wave speed (c) is calculated as the square root of gravitational acceleration (g) multiplied by the water depth (h).
How does basin geometry affect seiche periods?
The shape and size of the basin significantly influence the natural resonant frequencies, thus affecting the seiche period.
What is the significance of the fundamental seiche period?
The fundamental seiche period represents the lowest frequency at which a water body can oscillate, influencing its response to external disturbances like wind or earthquakes.
Results are for informational purposes only and do not constitute professional advice.