------
## 最终结论
```python
def max_vowels(s: str, k: int) -> int:
    max_vowel_count = 0
    current_vowel_count = 0

    for i in range(k):
        if s[i] in 'aeiou':
            current_vowel_count += 1
    max_vowel_count = current_vowel_count

    for i in range(k, len(s)):
        if s[i] in 'aeiou':
            current_vowel_count += 1
        if s[i - k] in 'aeiou':
            current_vowel_count -= 1
        max_vowel_count = max(max_vowel_count, current_vowel_count)

    return max_vowel_count
```