Üç boyutlu idealize bir İstanbul Boğazı hidrodinamik Modelinde Karadeniz Soğuk Ara Tabakası Zorlamasının Zaman Ölçeği Hassasiyeti

İstanbul Boğazı’nın hidrodinamiği üç boyutlu bir sayısal model marifetiyle idealize koşullar altında incelenmiş, Karadeniz’in soğuk ara tabakasının (SAT) basitleştirilmiş bir halinin idealize modelin kuzey sınırından penetrasyonu simule edilerek modelin açık sınır koşullarıyla gerçekleştirilen sıcaklık profili zorlamasının zaman ölçeğine (tnudg) hassasiyeti araştırılmıştır. SAT benzeri bir tabakanın boğaza pentrasyonu ancak bir günden küçük tnudg (sınırdan içeri) değerleri ile mümkün olmuş ve sınır-dışarı tnudg değerinin kuvvetinin önemsiz olduğu tespit edilmiştir. Bununla birlikte güçlü zorlama değerleri altında (tnudg ≤ 0.01) kuzey açık sınırında sayısal düzensizlikler meydan gelmiştir, bu da oldukça idealize edilmiş bir Boğaz modeli için bile SAT’ın başarılı simülasyonlarını için zorlama zaman ölçeğinin dikkatlice seçilmesi gerektiğini göstermektedir. İdealleştirilmiş kanalın kuzeyindeki sıcaklık dağılımını değiştiren SAT’ın varlığı, iki tabakalı değişim akımı üzerinde önemli bir etkiye sahiptir. Boğaz’ın kuzey kısmındaki stratifikasyonun değişimi ile kanalın iki ucu arasındaki yoğunluk farkı, ve buna istinaden alt ve üst tabaka akıları ve hızları azalmış olmakla birlikte, iki tabakalı yaklaşıma dayanan kuzey eşiğindeki hidrolik kontrol kaybolmamıştır.

Anahtar Kelimeler:

İstanbul Boğazı, Soğuk Ara Tabaka, İdealize 3b Model

Nudging Time-Scale Sensitivity of a Simplified Black Sea CIL Forcing with a Three-Dimensional Idealized Bosphorus Hydrodynamic Model

Hydrodynamics of the Bosphorus Strait is examined under idealized conditions with a three-dimensional numerical model. In particular, penetration of a simplified Cold Intermediate Layer (CIL) of the Black Sea into the Strait specifıed at the boundary is simulated with the aim of testing the sensitivity of the idealized model with respect to nudging strength. Successful penetration of a CIL-like stratification can only be achieved by inflowing nudging time-scales less than or equal to one day, while the outflowing nudging strength is found to be insignificant. However, numerical instabilities at the boundary are observed for strong nudging cases with tnudg ≤ 0.01 day suggesting that a careful selection of the nudging time-scale is important to achieve successful simulations of the CIL even in this highly idealized setup of the Bosphorus strait. The presence of CIL altering the temperature distribution within the northern section of the idealized channel has a significant impact on the exchange through the strait. CIL reduces the density difference across the strait resulting in decreased layer fluxes and velocities, while a two-layer sense hydraulic control still holds at the sill.

Keywords:

Bosphorus, Cold Intermediate Layer, Idealized 3d model,

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