# Daniel BanutiKarlsruhe Institute of Technology | KIT

Daniel Banuti

PhD Aerospace Engineering

## About

82

Publications

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## Publications

Publications (82)

This study investigates the spontaneous ignition of high-pressure hydrogen-enriched methane in air within a
rectangular tube. A computationally efficient approach has been adopted, utilizing a reduced reaction mechanism and ignition delay model within a 3D Large Eddy Simulation (LES) framework. This approach overcomes
the limitations of traditional...

Fluid blends as working fluids in solar thermal power cycles have been shown to promise an even higher efficiency than pure fluids. Rather than exploring specific blends, we propose an approach in which we directly optimize for a working fluid characterized in terms of the fluid critical point following the fundamental corresponding states principl...

Our understanding of supercritical fluids has seen exciting advances over the last decades, often in direct contradiction to established textbook knowledge. Rather than being structureless, we now know that distinct supercritical liquid and gaseous states can be distinguished and that a higher order phase transition - pseudo boiling - occurs betwee...

Clean energy generation is gaining significant attention from industries, academia, and governments across the globe. The Allam cycle is one such technology that has been under focus due to its efficiency, environmental friendliness, and economics. This is a direct-fired cycle operating at supercritical conditions using carbon dioxide as a working...

Clean energy generation is gaining significant attention from industries, academia, and governments across the globe. The Allam cycle is one such technology that has been under focus due to its efficiency, environmental friendliness, and economics. This is a direct-fired cycle operating at supercritical conditions using carbon dioxide as a working...

Flows in liquid propellant rocket engines (LRE) are characterized by high pressures and extreme temperature ranges, resulting in complex fluid behavior that requires elaborate thermo-physical models. In particular, cubic equations of state and dedicated models for transport properties are firmly established for LRE simulations as a way to account f...

In propulsion and power systems, operating pressures are increasing to improve cycle efficiency, often reaching conditions that approach or exceed the thermodynamic critical pressure of the working fluid. A known phenomenon that occurs at supercritical pressures is supercritical heat transfer deterioration (HTD). Although this phenomenon is well st...

In this paper, a dataset of wall-resolved large-eddy simulations of cryogenic hydrogen at supercritical pressure and different values of wall heat flux is presented. The aim is to provide a reference dataset for wall-function development under trans- and supercritical conditions, such as those found in liquid rocket engine applications. The employe...

We introduce Dynamic Constrained Grid (DCGrid), a hierarchical and adaptive grid structure for fluid simulation combined with a scheme for effectively managing the grid adaptations. DCGrid is designed to be implemented on the GPU and used in high-performance simulations. Specifically, it allows us to efficiently vary and adjust the grid resolution...

View Video Presentation: https://doi.org/10.2514/6.2022-0339.vid In this contribution a database of wall-resolved LES of cryogenic hydrogen at 5 MPa at different values of wall heat flux is presented. The employed numerical framework is a pressure-based segregated low-Mach number approach based on an equation-of-state independentformulation. The WA...

View Video Presentation: https://doi.org/10.2514/6.2022-0677.vid In many systems, from rocket engines to concentrated solar power, pressures are increased to increase efficiency, thus resulting in these systems operating at supercritical pressures. A crucial step in the design of rocket engines and power systems is to simulate these processes with...

Due to the complex interplay of various meteorological phenomena, simulating weather is a challenging and open research problem. In this contribution, we propose a novel physics-based model that enables simulating weather at interactive rates. By considering atmosphere and pedosphere we can define the hydrologic cycle - and consequently weather - i...

This paper introduces the hybrid ergodic lattice gas model as a conceptually simple, computationally cheap, yet accurate model that predicts macroscopic fluid pressure along the critical isotherm of a fluid accurately. A key concept is the hybrid evaluation of the properties: the kinetic and repulsive pressure components are calculated from equatio...

View Video Presentation: https://doi.org/10.2514/6.2021-3593.vid An important aspect for the design of rocket engines is the need to accurately model and simulate the injection and regenerative cooling processes. These processes typically occur at supercritical pressures. Modeling these processes with CFD is challenging, as it is hard to accurately...

Resulting from changing climatic conditions, wildfires have become an existential threat across various countries around the world. The complex dynamics paired with their often rapid progression renders wildfires an often disastrous natural phenomenon that is difficult to predict and to counteract. In this paper we present a novel method for simula...

Today, modern combustion systems and advanced cycles often reach operating pressures exceeding the working fluid’s or fuel’s critical pressure. While the liquid-gas coexistence line is the dominant feature in the fluid state space at low pressures, a supercritical analog to boiling, pseudo boiling, exists at supercritical pressures. Pseudo boiling...

Regenerative cooling in high-performance engines requires propellants to be at high pressures. Fluids under these supercritical conditions have drastic changes to their thermodynamic properties which can affect how they perform in the regenerative cooling process, including phenomena such as heat transfer deterioration. Modeling these processes wit...

Path finding is a common problem in computer science that has applications in robotics and autonomous systems and can be solved using reinforcement learning. Many solutions to path finding problems rely on the agent having full knowledge of its environment, however this may limit the agent from being able to act effectively in environments it has n...

Deep neural networks have found their way into a wide range of applications, with astound- ing success. Deeper and more complex networks are being developed, with hundreds of layers and intricate architectures. In this paper, we evaluate the opposite: how small can artificial neural networks (ANN) be and still accurately capture fluid properties th...

Supercritical fluid pseudo-boiling (PB), recently brought to the attention of the scientific community, is the phenomenon occurring when fluid changes its structure from liquid-like (LL) to gas-like (GL) states across the Widom line. This work provides the first quantitative analysis on the thermodynamics and the dynamics of water's PB, since the u...

The complex interplay of a number of physical and meteorological phenomena makes simulating clouds a challenging and open research problem. We explore a physically accurate model for simulating clouds and the dynamics of their transitions. We propose first-principle formulations for computing buoyancy and air pressure that allow us to simulate the...

The response of a transcritical oxygen-hydrogen flame to transverse acoustic velocity was investigated using a combination of experimental analyses and numerical modelling. The experiment was conducted on a rectangular rocket combustor with shear coaxial injectors and continuously forced transverse acoustic field. Simultaneous high-speed shadowgrap...

Fig. 1. Three types of thunderstorm supercells simulated with our framework: low precipitation supercell (le), a classical supercell (middle), and a high-precipitation supercell (right). The complex interplay of a number of physical and meteorological phenomena makes simulating clouds a challenging and open research problem. We explore a physically...

Experimental, computational, and theoretical results have shown that the notion of a homogeneous supercritical state space has to be replaced with distinct liquid-like and gas-like regions, divided by a cross-over line. Several such cross-over lines have been proposed, such as the Frenkel line, the Fisher-Widom line, and the Widom line. We use ther...

Simulations of fluid mixing occurring at high-pressures mandate the use of real-fluid equations of state to capture the effect of both intermolecular repulsive forces and attractive forces which are neglected in perfect gases. Dedicated mixing rules account for these forces by providing a generic mapping of the mixture state-space onto a pure fluid...

An experimental combustor, designated BKH, is operated at DLR Lampoldshausen to investigate high-frequency combustion instability phenomena. The combustor operates with liquid oxygen (LOx) and gaseous or liquid hydrogen propellants at supercritical conditions analogous to real rocket engines. An externally imposed acoustic disturbance interacts wit...

This paper derives from the cooperation between DLR and Airbus DS within the work package “CFD Modeling of Combustion Chamber Processes” conducted in the frame of the Propulsion 2020 project. In a joint strategy, DLR Göttingen and Airbus DS Ottobrunn have identified a number of test cases with gradually growing complexity where adequate test data a...

This paper derives from the cooperation between DLR and Airbus within the work package "CFD Modeling of Combustion Chamber Pro-cesses" conducted in the frame of the Propulsion 2020 project. In a joint strategy, DLR Göttingen and Airbus DS Ottobrunn have identified a number of test cases with gradually growing complexity where adequate test data are...

An experimental combustor, designated BKH, is operated at DLR Lampoldshausen to investigate high-frequency combustion instability phenomena. The combustor operates with liquid oxygen (LOx) and gaseous or liquid hydrogen propellants at supercritical conditions analogous to real rocket engines. An externally imposed acoustic disturbance interacts wit...

The article discusses the notion of a supercritical latent heat during 'pseudoboiling': Experimental, numerical, and theoretical evidence show that the supercritical state space is not homogeneous, but can be divided into liquid-like and gas-like domains, separated by an extension to the coexistence line -- the Widom line. The key concept are two l...

We investigate the flow in planar microscale nozzles and find that design and analysis paradigms based on the assumption of a dominant isentropic core with moderate viscosity corrections are not valid. Instead, the flow downstream of the throat is dominated by boundary layers that may choke the flow to subsonic velocities. The geometrical expansion...

In this study, we evaluate the thermodynamic structure of laminar hydrogen/oxygen flames at supercrit- ical pressures using 1D flame calculations and large-eddy simulation (LES) results. We find that the real fluid mixing behavior differs between inert (cold flow) and reactive (hot flow) conditions. Specifically, we show that combustion under trans...

The accurate and robust simulation of transcritical real-fluid flows is crucial for many engineering applications. Diffused interface methods are frequently employed and several numerical schemes have been developed for simulating transcritical flows. These schemes can be categorized into two types, namely fully conservative and quasi-conservative...

Recent experiments on pure fluids have identified distinct liquid-like and gas-like regimes even under supercritical conditions. The supercritical liquid-gas transition is marked by maxima in response functions that define a line emanating from the critical point, referred to as Widom line. However, the structure of analogous state transitions in m...

The coexistence line of a fluid separates liquid and gaseous states at subcritical pressures, ending at the critical point. Only recently, it became clear that the supercritical state space can likewise be divided into regions with liquidlike and gaslike properties, separated by an extension to the coexistence line. This crossover line is commonly...

An extension to the classical FPV model is developed for transcritical real-fluid combustion simulations in the context of finite volume, fully compressible, explicit solvers. A double-flux model is developed for transcritical flows to eliminate the spurious pressure oscillations. A hybrid scheme with entropy-stable flux correction is formulated to...

This paper introduces a new model for real gas thermodynamics, with improved accuracy, performance, and robustness compared to state-of-the-art models. It is motivated by the physical insight that in non-premixed flames, as encountered in high pressure liquid propellant rocket engines, mixing takes place chiefly in the hot reaction zone among ideal...

Certain experiments in quasi-isobaric supercritical injection remain unexplained by the current state of theory: Without developing a constant value potential core as expected from the mechanical view of break-up, density is observed to drop immediately upon entering the chamber. Furthermore, this phenomenon has never been captured in computational...

An experimental combustor, designated BKH, is operated at DLR Lampoldshausen to investigate high frequency combustion instability phenomena. The combustor operates with liquid oxygen and gaseous or liquid hydrogen propellants at supercritical conditions analogous to real rocket engines. An externally imposed acoustic disturbance interacts with a se...

Space transportation systems are exposed to high thermal and mechanical loads during the ascend in the transonic flow regime. By now, there are still many uncertainties, which can not be solved with state of the art computational fluid dynamic models or experiments with cold jet flows. A test facility with a high degree of similarity to flight with...

Recent publications in the open literature have shown that supercritical fluid states are not homogeneously distributed but, in fact, can be differentiated into two distinct regions with gas-like and liquid-like properties, respectively. These regions are divided by an extension of the coexistence line, commonly called Widom line. This paper shows...

Although liquid propellant rocket engines are operational and have been studied for decades, cryogenic injection at supercritical pressures is still considered essentially not understood. This thesis intends to approach this problem in three steps: by developing a numerical model for real gas thermodynamics, by extending the present thermodynamic v...

Injection of cryogenic nitrogen into a chamber at supercritical conditions has become a popular test case for real gas CFD validation. However, there is a systematic discrepancy: a measured immediate drop of density upon entering the chamber could not be found with theory or CFD. It is shown here that heat transfer to the cryogenic injectant does t...

This paper derives from the cooperation between DLR and Airbus DS within the work package "CFD Modelling of Combustion Chamber Processes" conducted in the frame of the Propulsion 2020 project. In a joint strategy, DLR Göttingen and Airbus DS Ottobrunn have identified a number of test cases with gradually growing complexity where adequate test data...

An experimental combustor, dubbed BKH, has been developed at DLR Lampoldshausen to investigate combustion instability phenomena. The combustor operates with cryogenic liquid oxygen and hydrogen propellants at supercritical pressure conditions analogous to real rocket engines. The BKH combustor has been modelled using a specially developed version o...

In this paper, a new interpretation of cryogenic jet break-up in supercritical environments is introduced. It is firmly established that under these conditions a pure fluid will exhibit neither latent heat of vaporization nor surface tension. The jet undergoes a transition from a dense cryogenic fluid to an ideal gas as it mixes and blends with the...

In this paper we report on supercritical single injector computations using a new type of real gas CFD model. This Euler-Euler model is an extension to the DLR TAU CFD code. By storing fluid data in a library, we were able to decouple equation of state (EOS) accuracy from runtime performance. The library covers all fluid states efficiently and robu...

Flow in micro chemical propulsion systems ($\mu$CPS) based on etched silicon deviates strongly from its conventional, macroscopic counterparts. This paper reports on peculiarities of small scale planar nozzles with a high aspect ratio, rectangular cross section. Design and analysis paradigms based on the assumption of rationally symmetric flow with...

This paper reports on a new kind of real gas model, particularly suited for rocket injection applications. It differs from state-of-the-art models in two main ways: First, we use a precomputed library to store fluid data, instead of equation of state evaluation during runtime. Second, a newly developed multi-fluid-mixing model solves an individual...

Regarding current trends in the miniaturization of satellites, an appropriate propulsion system is sought. Within the EU project PRECISE, a system analysis has shown that a MEMS (micro-electro-mechanical system) monopropellant hydrazine thruster has the potential to deliver thrust and Isp on a level that cannot be matched by other microsystems (e.g...

PRECISE focuses on the research and development of a MEMS-based monopropellant micro chemical propulsion system for highly accurate attitude control of satellites. The design of the μCPS is not comparable to common propulsion systems since the MEMS-based chips from the μValve over the μThruster to the μCatalyst demand a radically different system d...

In this paper we introduce a novel model for liquid rocket engine (LRE) propellant injection. Most academic codes today use an Eulerian-Eulerian (EE) description, i.e. all involved propellants and reaction products are regarded as continuous uids instead of discrete droplets. These models have successfully been improved and are capable of high fide...

Design of a hot plume testing facility for ELV propulsion characterization

This paper discusses a thermodynamic rather than mechanic discussion and interpretation of cryogenic injection of nitrogen in the vicinity of the critical point. There is no concensus in the literature on how to properly interpret and treat injection phenomena at supercritical pressures. While it is clear that the supercritical fluid loses many dis...

This paper discusses features of a supersonic flow with a transversal Mach number stratification when encountering a ramp. A flow of this nature can occur for a variety of reasons around a hypersonic vehicle. Formation of a heated wall boundary layer, external fuel injection on the compression ramp, energy deposition, and film or transpiration cool...

This paper discusses the ongoing extension of the DLR TAU Code with a multiphase flow model. The reasoning behind choosing a Statistical Eulerian Eulerian (SEE) model with Interfacial Area Transport Equation (IATE) is covered. Properties of the model are introduced, especially concerning the less known IATE concept which provides information about...

This paper reports on numerical investigation and discussion of a cryogenic injection test case. This is a first step towards a numerical model for high pressure liquid rocket engine injection. Experiments with nitrogen injection at supercritical pressures are an accepted way of studying flow phenomena relevant for high pressure liquid rocket engin...

This paper discusses some general properties of energy deposition in hypersonics. Extending the flight envelope of passenger aircraft to high Mach numbers comes with problems unsolved before in civil flight, such as sonic boom, or excessive thermal and mechanical loads. Energy deposition is regarded as a possible remedy to a multitude of problems o...

This paper discusses the ongoing extension of the DLR TAU Code with a multiphase flow model. The reasoning behind choosing a Statistical Eulerian Eulerian (SEE) model with Interfacial Area Transport Equation (IATE) is covered. Properties of the model are introduced, especially concerning the less known IATE concept which provides information about...

This paper discusses the application of energy deposition for sonic boom mitigation and as actuator device substitute. Classical sonic boom minimization strategies suffer from major shortcomings, such as prohibitively large power requirements or a permanent deterioration of aerodynamic quality - even when sonic boom suppression is not needed. Virtu...

A conceptual study is here presented and discusscd on the possibility to transport 200 passengers over a distance of about 7000km in a nominal point-to-point mission through the Atlantic (either London-New York or London-Rio) at a cruise Mach number of 6 and an altitude abont 30km. The aim of the study is not to design a specific airplane but to ex...

Contributions to Statistical Eulerian-Eulerian (SEE) flow models of two-phase flow are discussed in this article. Special attention is given to the Interfacial Area Transport Equation (IATE) which allows for sub grid scale modeling of exchange processes and a topological interpretation of continuous results. An interfacial area convection velocity...