Coalescence

Header file: <libs/superdrops/collisions/coalescence.hpp> [source]

inline bool is_null_superdrop(const Superdrop &drop)

Raises an error if the multiplicity of the super-droplet is 0.

This function checks if the given superdrop is null by verifying its multiplicity. It asserts that the multiplicity (xi) of the superdrop is greater than 0. If the multiplicity is 0, an assertion error is raised.

Parameters:

drop – A reference to the Superdrop object to be checked.

Returns:

Always returns 0 (=false).

struct DoCoalescence

Public Functions

bool operator()(Superdrop &drop1, Superdrop &drop2, const double prob, const double phi) const

Operator used as an adaptor such that DoCoalescence satisfies the PairEnactX concept and so can be used as the EnactCollision function-like object in the DoCollisions struct.

This operator calls functions to enact the collision-coalescence of two super-droplets.

Parameters:

  • drop1 – The first super-droplet.

  • drop2 – The second super-droplet.

  • prob – The probability of collision-coalescence.

  • phi – Random number in the range [0.0, 1.0].

Returns:

boolean=true if collision-coalescence resulted in null superdrops.

uint64_t coalescence_gamma(const uint64_t xi1, const uint64_t xi2, const double prob, const double phi) const

Calculates the value of the gamma factor in Monte Carlo collision-coalescence.

This function calculates the value of the gamma factor used in Monte Carlo collision-coalescence as described in Shima et al. 2009.

Parameters:

  • xi1 – The multiplicity of the first super-droplet.

  • xi2 – The multiplicity of the second super-droplet.

  • prob – The probability of collision-coalescence.

  • phi – Random number in the range [0.0, 1.0].

Returns:

The calculated value of the coalescence gamma factor.

bool coalesce_superdroplet_pair(const uint64_t gamma, Superdrop &drop1, Superdrop &drop2) const

Coalesces a pair of superdroplets.

This function coalesces a pair of superdroplets by changing their multiplicity, radius, and solute mass according to Shima et al. 2009 Section 5.1.3. part (5).

Parameters:

  • gamma – The coalescence gamma factor.

  • drop1 – The first superdroplet.

  • drop2 – The second superdroplet.

Returns:

True if coalescence results in a null superdroplet, false otherwise.

Private Functions

void twin_superdroplet_coalescence(const uint64_t gamma, Superdrop &drop1, Superdrop &drop2) const

Enacts coalescence of a pair of superdroplets where xi1 = gamma*xi2.

This function coalesces a pair of superdroplets where drop1.get_xi() = gamma* drop2.get_xi() by making twin superdroplets with the same xi, radius, and solute mass. It implements Shima et al. 2009 Section 5.1.3. part (5) option (b).

In rare case where xi1 = xi2 = gamma = 1, new_xi of drop1 = 0 and drop1 should be removed from domain.

Note: Implicit casting of gamma (and therefore droplets’ xi values) from uint64_t to double.

Parameters:

  • gamma – The coalescence gamma factor.

  • drop1 – The first superdroplet.

  • drop2 – The second superdroplet.

void different_superdroplet_coalescence(const uint64_t gamma, Superdrop &drop1, Superdrop &drop2) const

Coalesces a pair of superdroplets where xi1 > gamma*xi2.

This function coalesces a pair of superdroplets where xi1 > gamma*xi2 by growing the radius and mass of drop2 via decreasing the multiplicity of drop1. It implements Shima et al. 2009 Section 5.1.3. part (5) option (a).

Note: Implicit casting of gamma (i.e. therefore droplets’ xi values) from uint64_t to double.

Parameters:

  • gamma – The coalescence gamma factor.

  • drop1 – The first superdroplet.

  • drop2 – The second superdroplet.

template<PairProbability Probability>
inline MicrophysicalProcess auto CollCoal(const unsigned int interval, const std::function<double(unsigned int)> int2realtime, const Probability collcoalprob)

Constructs a microphysical process for collision-coalescence of superdroplets.

This function constructs a microphysical process for collision-coalescence of superdroplets with a constant timestep and probability of collision-coalescence determined by ‘collcoalprob’.

Template Parameters:

Probability – Type satisfying the PairProbability concept.

Parameters:

  • interval – The constant timestep interval.

  • int2realtime – A function that converts an integer timestep to real time.

  • collcoalprob – The probability of collision-coalescence.

Returns:

An instance of MicrophysicalProcess for collision-coalescence.