Advanced Physics / Electrohydrodynamics / Experimental Propulsion Systems

Capacitor with Electrohydrodynamic Flow through Corona Discharge

At AWJ Engineering, our team investigated the impact of ground electrode width on propulsion generated by an asymmetric capacitor, which induces electrohydrodynamic (EHD) flow via corona discharge in nitrogen gas at atmospheric pressure. Our numerical model incorporated electrostatic force interactions between electrodes and ion space clouds, momentum exchange with the induced nitrogen flow, pressure forces, and viscous drag, ensuring a comprehensive simulation of real-world dynamics.

The client provided an initial model plagued by grid-dependent results. We conducted dual parametric sweeps on mesh parameters, including maximum element sizes for FEA and CFD domains, to eliminate grid dependency. By optimizing solver settings, we achieved highly accurate validation against established benchmarks (e.g., Martins' research).

For details on the grid independence study or to discuss similar challenges, contact us today.

Surface plot of electric field in the corona discharge capacitor simulation

◀ Contour plot of electrohydrodynamic flow around the asymmetric capacitor, COMSOL simulationSurface plot of electric field in the corona discharge capacitor simulation ▶

Industry: Advanced Physics / Electrohydrodynamics / Experimental Propulsion Systems
Client Type: Research organization developing electrohydrodynamic propulsion technologies
Service Provided: Multiphysics simulation and numerical validation
Objective: Analyze the effect of ground electrode width on propulsion generated by an asymmetric capacitor
Engineering Method: Coupled electrostatic, fluid dynamics and PDE Modules
Simulation Platform: COMSOL Multiphysics
Core Focus: Corona discharge-induced electrohydrodynamic (EHD) airflow and thrust generation

The Client

The client was conducting research into electrohydrodynamic (EHD) propulsion systems, an emerging technology that generates thrust by accelerating ionized air particles through electric fields.

In asymmetric capacitor configurations, high-voltage corona discharge creates ion space clouds that interact with surrounding air molecules. As ions accelerate toward the ground electrode, they transfer momentum to neutral gas molecules, producing airflow commonly referred to as ionic wind.

This phenomenon has promising applications in:

silent propulsion technology
advanced airflow control systems
experimental aerospace research
energy-efficient cooling mechanisms

To advance their research, the client needed to evaluate how changes in electrode geometry-specifically the width of the ground electrode-affect propulsion performance.

The Challenge

Electrohydrodynamic propulsion systems involve complex interactions between electric fields, ion transport, and fluid flow.

Key research questions included:

how electrode geometry influences electric field distribution
how ion space clouds interact with surrounding gas molecules
how momentum transfer generates airflow and thrust
how system performance changes as electrode dimensions vary

The client had previously developed a numerical model to study these effects. However, the results were highly dependent on mesh resolution, making it difficult to ensure simulation accuracy and reliability.

Grid-dependent results can significantly distort Multiphysics simulations, leading to incorrect predictions of flow velocity, thrust generation, and pressure forces.

The client therefore required a robust computational approach that could eliminate grid dependence while accurately capturing electrohydrodynamic behavior.

Engineering Challenge

Modeling EHD propulsion systems requires coupling multiple physical phenomena within a single computational framework.

The simulation needed to simultaneously capture:

electrostatic forces between electrodes
ion transport and charge distribution
momentum exchange between ions and neutral gas molecules
airflow behavior induced by ionic wind
pressure forces and viscous drag within the gas domain

Achieving stable and reliable results required careful handling of mesh resolution, solver settings, and Multiphysics coupling.

Ensuring grid independence was particularly critical to validating the simulation results against established research.

Our Approach

AWJ Engineering implemented a structured simulation and validation workflow to address the client's modeling challenges.

Model Review and Problem Diagnosis

Our team began by reviewing the client's existing numerical model to identify the source of grid-dependent behavior.

Initial analysis revealed that mesh parameters within both the finite element electrostatic domain and the computational fluid dynamics domain were contributing to inconsistent results.

Multiphysics Simulation Framework

The system was modeled as a coupled Multiphysics problem involving

electrostatic interactions between electrodes

ion space cloud dynamics

momentum transfer between charged particles and nitrogen gas

airflow generation driven by electrohydrodynamic forces

The simulation accounted for the primary forces acting within the system, including:

electrostatic force interactions
pressure forces within the fluid domain
viscous drag within the nitrogen flow

Grid Independence Study

To eliminate grid dependence, our team conducted two parametric sweeps on mesh parameters.

These sweeps focused on:

maximum element size within the finite element analysis (FEA) domain
minimum element size within the finite element analysis (FEA) domain
maximum element size within the computational fluid dynamics (CFD) domain
minimum element size within the computational fluid dynamics (CFD) domain

This systematic approach ensured that the simulation results remained stable regardless of mesh refinement.

Solver Optimization

Beyond mesh adjustments, we optimized solver settings to improve numerical stability and convergence across the coupled physical models.

This step was essential for accurately capturing the interactions between electric fields and airflow dynamics.

Model Validation

Once grid independence was achieved, the simulation results were compared against established experimental and numerical benchmarks, including research conducted by Martins and other researchers in electrohydrodynamic propulsion.

This validation confirmed that the simulation framework produced reliable and physically accurate results.

The Solution

Through careful mesh optimization and solver refinement, AWJ Engineering successfully developed a stable Multiphysics simulation of the asymmetric capacitor system.

The final model enabled detailed analysis of:

electric field distribution across the electrodes
ion space cloud formation and behavior
induced airflow velocity in nitrogen gas
thrust generation resulting from electrohydrodynamic forces

By resolving the grid dependency issues, the simulation provided the client with a reliable computational framework for studying electrode geometry effects on propulsion performance.

This framework can now be used to explore further design variations and optimize future EHD propulsion systems.

Technologies Used

Multiphysics Modeling: Electrostatic, Fluid Dynamics and PDE Module coupling
Numerical Methods: Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD)
Simulation Focus: Electrohydrodynamic airflow modeling, Ion transport dynamics, Momentum exchange between ions and gas molecules
Validation Method: Benchmark comparison with established electrohydrodynamic research

Results & Business Impact

The project delivered a robust and validated simulation model capable of accurately analyzing EHD propulsion systems.

Key outcomes included:

elimination of grid-dependent simulation behavior
validated numerical framework for electrohydrodynamic analysis
improved understanding of airflow generation through corona discharge
reliable evaluation of electrode geometry effects on propulsion
enhanced confidence in simulation-based research for EHD technologies

With this improved modeling framework, the client can now investigate new electrode configurations and propulsion concepts with greater accuracy and reduced experimental costs.

Key Takeaways

This project highlights AWJ Engineering's expertise in advanced Multiphysics simulations involving electrostatics, fluid dynamics, and ion transport phenomena.

Our engineering capabilities enable clients to:

solve complex numerical modeling challenges
eliminate instability in simulation results
validate experimental research through computational methods
accelerate development of advanced physical technologies

By combining deep simulation expertise with rigorous validation methods, AWJ Engineering helps organizations transform complex theoretical concepts into reliable engineering insights.

Simulation results