Dhi Mike 21 ((free))

MIKE 21 is a premier 2D modeling system developed by the Danish Hydraulic Institute (DHI) used to simulate physical processes in water environments like oceans, estuaries, and rivers. It is widely considered the industry standard for coastal engineering and oceanography due to its ability to handle complex free-surface flows where vertical stratification is not a primary factor. Core Capabilities & Modules

The software is modular, allowing users to customize simulations based on specific environmental needs:

Hydrodynamics (MIKE 21 HD): The engine that simulates water level variations and flows in response to forcing functions like tides, wind, and river discharge.

Spectral Waves (MIKE 21 SW): A state-of-the-art model for simulating the growth, decay, and transformation of wind-generated waves and swells in both offshore and coastal areas.

Sand Transport (MIKE 21 ST): Used to calculate littoral drift and sediment transport, which is essential for studying beach erosion and harbor siltation. dhi mike 21

Water Quality (ECO Lab): Integrates with the hydrodynamic module to simulate water quality reaction processes, such as nutrient cycles or pollutant dispersion. Key Technical Features

Understanding DHI MIKE 21: The Global Standard for 2D Water Modeling

MIKE 21, developed by the Danish Hydraulic Institute (DHI), is a premier computer program used to simulate two-dimensional free-surface flows where stratification can be neglected. It is widely recognized by engineers and scientists worldwide for its accuracy in modeling rivers, lakes, estuaries, and coastal areas. Core Capabilities and Features

MIKE 21 operates as a modular system, allowing users to select specific tools tailored to their project needs. Its primary strength lies in its ability to simulate water level changes and flows in response to various forces, including tides, wind, and river inflows. MIKE 21 is a premier 2D modeling system

The following overview explores the capabilities and applications of MIKE 21, a premier 2D numerical modeling system developed by DHI for simulating hydrodynamics, waves, and sediment transport in marine and coastal environments. Core Modeling Principles

MIKE 21 is a two-dimensional, depth-averaged modeling system designed for free-surface flows. It operates by solving the depth-integrated Reynolds-averaged Navier-Stokes equations, which account for the conservation of mass and momentum. Grid Types:

Classic: Uses a structured, orthogonal rectangular grid suitable for straightforward bathymetries.

Flexible Mesh (FM): Utilizes an unstructured mesh (typically triangles or quadrilaterals), allowing for higher resolution in critical areas like coastlines or around structures while maintaining coarser resolution in the deep ocean. Industry Standard: Accepted by regulators worldwide

Key Physics: The engine simulates factors such as bottom shear stress, Coriolis force, momentum dispersion, and wind fields. MIKE 21-3 | Coast and Marine Water Modelling Software - DHI

Pros:

• Industry Standard: Accepted by regulators worldwide.
• Coupling: Seamless integration of waves, flows, and sediments.
• Flexible Mesh: Allows for high-resolution modeling around structures without slowing down the whole domain.
• Documentation: Excellent scientific documentation and user guides.
• DHI Support: Access to professional support engineers (if you have a maintenance contract).

Key Modules and Applications

MIKE 21 is not a single tool but an integrated suite of modular engines, each designed to tackle a specific physical or environmental process. The most fundamental is the Hydrodynamic (HD) Module, which computes water levels and flow velocities. Upon this foundation, users can activate additional modules:

• MIKE 21 SW (Spectral Waves): This module simulates the generation, propagation, and dissipation of wind-generated waves. It is indispensable for designing coastal defenses, predicting wave agitation in harbors, and assessing the impact of wave energy on shorelines.
• MIKE 21 MT (Mud Transport) and ST (Sand Transport): These modules model the erosion, transport, and deposition of cohesive (mud) and non-cohesive (sand) sediments. Applications range from dredging impact assessments and port siltation studies to understanding long-term coastal morphology and beach evolution.
• MIKE 21 ECO Lab: This is a powerful water quality and ecological modeling framework. It allows users to simulate complex biogeochemical processes, including eutrophication, oxygen depletion, bacterial decay (e.g., E. coli), and algal blooms. It is crucial for managing wastewater discharge, protecting drinking water sources, and restoring aquatic ecosystems.
• MIKE 21 Oil Spill and Advection-Dispersion Modules: These tools model the fate and transport of contaminants or oil spills, accounting for weathering processes like evaporation, emulsification, and shoreline interaction. They support emergency response planning and environmental risk assessment.

Core Scientific & Engineering Foundation

MIKE 21 is built on robust numerical methods:

• Spatial Discretization: Uses a cell-centered finite volume method on a flexible mesh. This allows for:
  • Unstructured mesh: Triangular and quadrilateral cells to fit complex coastlines, islands, and structures.
  • Structured mesh (rectangular): For simpler, large-scale domains.
• Time Integration: Employs an explicit, high-order scheme (e.g., Runge-Kutta) for shallow water equations.
• Hydrodynamic Engine: Solves the depth-integrated Reynolds-Averaged Navier-Stokes (RANS) equations in 2D (the Saint-Venant equations for shallow water), including:
  • Non-linear advection terms.
  • Baroclinic density gradients (due to temperature/salinity).
  • Coriolis force.
  • Wind shear and atmospheric pressure.
  • Bottom friction (Manning, Chezy, Nikuradse).
  • Eddy viscosity (Smagorinsky, k-ε).
• Wetting and Drying: Handles intertidal zones and floodplains with robust algorithms.

DHI MIKE 21: The Industry Standard for 2D Hydrodynamic and Marine Modelling

Getting Started with DHI MIKE 21

If you are new to MIKE 21, follow this path:

1. Training: DHI offers a 3-day “Introduction to MIKE 21” course (often online or at their offices in Denmark, Singapore, USA, Australia). Many universities also teach it in coastal engineering masters programs.
2. License: Contact DHI or an authorized reseller. Options include:
   • Full license (perpetual + annual maintenance)
   • Rental (monthly or yearly)
   • Educational (discounted for universities)
3. Hardware: Recommend a workstation with multicore CPU (16+ cores), 32+ GB RAM, and fast SSD. For large coastal domains, consider cloud HPC (AWS or Azure).
4. Data sources:
   • Bathymetry: GEBCO (30 arc-sec), EMODnet, or local surveys.
   • Tides: TPXO9, FES2014, or harmonic constituents from tidal gauges.
   • Wind: ERA5 reanalysis (hourly, 0.25°).

A simple first model: Model wind-induced setup in a closed rectangular lake. Force with constant wind, set a weir at outflow, and compare water level slope to analytical solution.