Answer:
Assonance
Step-by-step explanation:
Assonance illustrates the repetition of similar or identical vowel sounds in literature or poetry that creates an internal rhyme between the phrases or sentences. It is usually employed either to establish the mood of the poem or enforce certain meanings or messages. In the excerpt from H.D.'s "heat", the figure of speech demonstrated is "assonance" in the words "O wind, rend open the heat, cut apart the heat, rend it to tatters' as the vowel sounds are being repeated within the phrase that create an internal rhyme.